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PENNSYLVANIA  GLACIATION 
FIRST  PHASE 


MATERIALS  FOR  A  DISCUSSION  OF  THE  ATTENUATED  BORDER 

OF  THE   MORAINE  DESCRIBED  IN  VOLUME  Z   OF   THE 

SECOND  GEOLOGICAL  SURVEY  OF  PENNSYLVANIA 


BY 

EDWARD  HIGGIINSOIN  WILLIAMS,  Jr, 

E.  M.,  Sc.  D.,  LL.  D.,  P.  G.  S.  A. 

LECTURER  ON   MINING  AND  GEOLOGY 

IN  LEHIGH   UNIVERSITY 


WOODSTOCK,  VERMONT 

1917 


PENNSYLVANIA  GLACIATION 
FIRST  PHASE 


PENNSYLVANIA  GLACIATION 
FIRST  PHASE 


MATERIALS  FOR  A  DISCUSSION  OF  THE  ATTENUATED  BORDER  OF 

THE  MORAINE  DESCRIBED  IN  VOLUME  Z  OF  THE  SECOND 

GEOLOGICAL  SURVEY  OF  PENNSYLVANIA 


BY 
EDWARD  HIGGINSON, WILLIAMS,  JR., 

E.  M.,  Sc.  D.,  LL.  D.,  F^G.  S.  A. 

LECTURER  ON  MINING  AND  GEOLOGY 
IN   LEHIGH   UNIVERSITY 


WOODSTOCK,  VERMONT 

1917 


EARTH 

SCIENCE^/ 

LIBRARY 


COPYRIGHT,  1917,  BY 
EDWARD  H.  WILLIAMS,  JR. 


»°  ',**  .  -.••.*   -j        5 '    ',. 

•    *  * 


THE  MAPLE  PRESS  YORK  PA 


PREFACE 

A  revision  of  previous  work  on  the  Attenuated  Border  became  impera- 
tive when  it  was  found  that  "drift"  could  consist  of  pieces  neither  rolled, 
glaciated  nor  moved  from  an  outcrop,  but  merely  disturbed  by  the 
advance  of  the  First  Phase  of  the  glacier,  which  brought  nothing  foreign. 

The  glacial  striae  are  associated  with  the  regional  troughs  along 
which  this  Phase  moved  towards  and  upon  Pennsylvania  in  the  form  of 
low  and  weak  lobes,  and  over  which  the  greatest  motion  obtained  during 
the  Mature  Phase.  The  outcrops  crossed  furnished  a  check-list  of  prob- 
able rocks  in  the  drift.  The  drainage  lines  marked  where  each  lobe  lost 
some  of  its  basal  burden.  The  origin  of  the  stony  gravel  was  solved. 
These  criteria  agreed  with  President  T.  C.  Chamberlin's  assumption  of  a 
Labrador  glacier  moving  to  Illinois. 

Native  copper  and  crystalline  rocks  are  found  only  in  the  extreme 
eastern  and  western  parts  of  Pennsylvania  in  the  drift  of  this  Phase.  In 
both  localities  floating  ice  seems  to  have  played  an  important  part.  With 
no  intention  of  claiming  a  Lake  Superior  origin  for  the  Connecticut  and 
Eastern  Pennsylvania  copper,  the  latter  can  not  come  from  the  Trias 
entirely,  as  it  is  found  in  Monroe  County,  north  of  Kittatinny  Mountain. 
Western  Pennsylvania  copper  certainly  has  a  Keewatin  origin,  and  the 
specimen  was  berg-carried. 

As  the  surface  of  Mohawk  Valley  is  everywhere  below  500  feet  above 
ocean  level,  and  as  Central  New  York  was  flooded  far  above  that  eleva- 
tion, ice-cakes  could  have  floated  into  the  Hudson  without  insisting  upon 
an  extension  of  Professor  Spencer's  Erigan  trough  thither,  and  the 
assumption  of  his  rock-floor  levels  north  of  Potter  County,  Penna.,  has  no 
bearing,  on  a  Hudson  outlet. 

The  mining  engineer  will  find  something  of  interest  in  the  " mucking" 
of  60  feet  of  slate  outcrop,  by  which  the  merchantable  product  is  quarried 
beneath  loose  drift.  The  mining  of  anthracite  with  the  highest  of  carbon 
ratios  from  beneath  glacial  gravel  is  interesting  as  showing  that  an  ex- 
posure of  many  thousand  years  has  no  appreciable  effect  on  this  coal. 

Thanks  are  due  to  the  members  of  the  classes  in  geology  at  Lehigh 
University  for  aid  during  the  reconnaissances  of  the  summer  vacations,  and 
especially  for  accurate  lines  of  level;  to  my  former  assistants,  Drs.  Joseph 
Barrell  and  Herman  E.  Kiefer  who  traversed  the  entire  Border  between 
the  Delaware  and  Allegheny  rivers;  to  the  Director  of  the  United  States 
Geological  Survey  for  permission  to  use  the  relief  map  (frontispiece)  as  a 
basis  for  tracing  the  great  moraine  and  the  boundary  of  the  Border,  and  to 
my  friends,  Professors  G.  Frederick  Wright  and  Benjamin  L.  Miller  for 

359664 


Vl  PREFACE 

valued  assistance  and  criticism.     The  following  papers  are  frequently 
referred  to.*  EDWARD  H.  WILLIAMS,  JR. 

WOODSTOCK,  VERMONT, 
February,  1,  1917. 


*(A)  Leverett,  F.,  Monograph  XLI,  U.  S.  Geol.  Surv.,  1902. 

(#)  Williams,  E.  H.  Jr.,  Extramorainic  Drift  between  the  Delaware  and  the 
Schuylkill,  Bull.  Geol.  Soc.  Amer.,  vol.  v,  pp.  281-296,  1893. 

(C)  Ibid.  The  Age  of  the  Extra-Moraine  Fringe  in  Eastern  Pennsylvania,  Amer. 
Jour.  Sci.,  vol.  xlvii,  pp.  32-36,  Jan.,  1894. 

(D)  Ibid.  Notes  on  the  Southern  Ice  Limit  in  Eastern  Pennsylvania,  ibid.,  vol. 
xlix,  pp.  174-185,  March,  1895. 

(E)  Ibid.  Notes  on  Kansan  Drift  in  Pennsylvania,  Proc.  Amer.  Philos.  Soc.,  vol. 
xxxvii,  No.  157,  April,  1898. 

(F)  Ibid.  Kansan  Glaciation  and  its  Effects  on  the  River  Systems  of  Northern 
Pennsylvania,  Proc.  &  Collect.  Wyoming  (Pa.)  Histor-Geol.  Soc.,  vol.  vii, 
Jan.,  1902. 

(<7)  Wright,  G.  Frederick,  The  Ice  Age  in  North  America,  5th  ed.,  1911. 


CONTENTS 

INTRODUCTION 

CHAPTER  I 

PAGES 

TOPOGRAPHY 1-6 

Influence  of  Pennsylvania  Geology  on  Topography;  Topography  of 
the  Region  north  and  east  of  Pennsylvania;  Elevation  of  the  Pennsyl- 
vania Plateau  above  Spencer's  Erigan  Trough;  Frontal  Attack  of 
Pennsylvania  by  Five  Glacial  Lobes;  Covering  of  Northwestern 
Pennsylvania  by  the  Lateral  Margin  of  the  Main  Ice-Sheet;  Routes  of 
Eight  Glacial  Lobes. 

CHAPTER  II 

THE  FIRST  PHASE 6-10 

Characteristics  of  a  First  Phase  of  Glaciation;  Basal  Depletion  as 
an  adjunct  in  forming  Rock  Cities;  Marginal  Crenatures;  Ability  to 
cross  Ridges;  Surface  slopes  of  Pennsylvania  lobes;  Lewis  &  Wright's 
Moraine  as  a  Curve  of  Work;  Relation  between  this  Moraine  and  the 
Attenuated  Border. 

CHAPTER  III 

THE  FLUVIAL  FORCES 11-13 

Classification  in  Streams;  Preglacial  Trenching  of  Stream  Bottoms; 
Ponding  and  Glacial  Lakes;  Col-trenching. 

CHAPTER  IV 

DRIFT  OK  THE  FIRST  PHASE 13-23 

Area;  Definition  of  Drift;  Approximation  to  Local  Outcrops;  Barren- 
ness of  Frontal  Base;  Criteria;  Data  of  Ageing  of  Drift;  Preglacial 
Rustiness,  Limonite;  Deforestation  as  a  Reducing  Agent;  Date  of  the 
Sculpturing  of  Deposits;  Rates  of  Decay  in  Rocks;  Suggested  Divi- 
sions of  Pennsylvania  Drift;  Table  of  Formations  for  Eastern  and 
Western  Pennsylvania. 

THE  ATTENUATED  BORDER 
CHAPTER  V 

G  REAT  VALLEY  DRIFT.    LOBE  3 25-43 

Durham  &  Reading  Hills;  Great  Valley  of  Pennsylvania;  Glacial  Lake 
Packer;  Kittatinny  Mountain;  The  Valleys  North  of  Kittatinny 
Mountain. 


viii  CONTENTS 

CHAPTER  VI 

PAGE 

BROAD  MOUNTAIN  DRIFT.    LOBE  2 43-54 

The  Strippings;  Comparison  of  Coals;  Southern  Anthracite  Basin; 
Conglomerate  Anticlinal;  Middle  Anthracite  Basin;  Western  Middle 
Basin;  Spoon-end  of  Shamokin  Basin. 

CHAPTER  VII 

SUSQUEHANNA  DRIFT.       LOBE  6 54-60 

The  North  Branch;  The  Main  Valley;  Middle  Creek  Valley;  Jacks 
Mountain;  Penns  Creek. 

CHAPTER  VIII 

PLATEAU  DRIFT.     LOBE  7 60-70 

Penns  Valley  to  Nittany  Valley;  Sunbury  to  Keating;  Sinnemahoning 
Creek;  Glacial  Lake  Lesley. 

CHAPTER  IX 

HIGHLAND  DRIFT.    LOBE  8 70-71 

Clarion  River  Headwaters;  Potter-McKean  County  Plateau. 

CHAPTER  X 

FLUVIATILE  DRIFT.     SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 72-101 

The  Geology  and  Present  Topography;  Preglacial  Topography  and  the 
Cols;  Lake  Wright;  Conewango  Slack  Water;  Lake  Leverett;  The 
Border  of  the  Ice-Sheet. 


LIST  OF  ILLUSTRATIONS 

Relief  Map  of  Pennsylvania  showing  the  great  moraine  and  the  boundary  of  the 
Attenuated  Border .    .   .    .    ..  .    ...    .    .    .    .    .    .;  .    .  Frontispiece 

FIG.  PAGE 

1.  Brownish-red  silt  including  quartzite  cobbles,  Bingen,  Northampton  Co.  15 

2.  Cutting  through  bar,  West  Bethlehem  gravels,  Northampton  Heights 16 

3.  Outwash  of  Lake  Lesley,  Dix  col,  Blair  Co 16 

4.  Reddish  silt  including  local  and  foreign  gneiss,  Riegelsville,  Nhn.  Co 25 

5.  Moraine  traversed  by  Saucon  Creek,  near  Bingen,  Nhn.  Co 26 

6.  Brownish-red  silt  including  quartzite,  gneiss,  Triassic  red  shale,  railroad 

cutting  south  of  Center  Valley,  Nhn.  Co 27 

7.  Mass  of  Oriskany  sandstone  showing  casts  of  Spirifer  arenosus,  Friedensville, 

Nhn.  Co.,  part  of  moraine  across  Saucon  Valley 27 

8.  Lower  Helderberg  pebble  (beneath  arrow)  in  gneiss  sand  on  col  of  South 

Mountain  southwest  of  South  Bethlehem,  Nhn.  Co 28 

9.  Pile  of  trap  cobbles  taken  from  drift  of  gneiss  and  quartzite,  near  crest  of 

South  Mountain,  South  Bethlehem,  Nhn.  Co 28 

10.  Merchantable  slate  beneath  drift,  Siegfried's,  ibid 29 

11.  Cutting  in  Hudson  slate  decaying  in  place,  between  Shoemakers ville  and 

Hamburg,  Berks  Co 31 

12.  Cutting  in  drift  of  slate  flakes  enclosing  polished  sandstone  boulders  and 

cobbles,  300  feet  south  of  last  figure,  Shoemakersville 31 

13.  Drift  at  extreme  edge  of  ice-sheet,  Centerport,  Berks  Co 32 

14.  West  Bethlehem  gravels  overlaid  unconformably  by  Packer  Clay,  Rauch's 

Pit,  West  Bethlehem,  Lehigh  Co . 36 

15.  Packer  Clay,  Brick-yard,  Bethlehem,  Nhn.  Co 38 

16.  Packer  Clay,  Brick-yard,  East  Allentown,  Lehigh  Co 38 

17.  Packer  Clay,  on  kame,  60  feet  above  Lehigh  River,  Stemton,  Nhn.  Co., 

including  polished  Pocono  cobbles  (iceberg  burden) 39 

18.  Accumulation  of  Oneida  conglomerate  masses  where  working  face  of  glacier 

crossed  Kittatinny  Mountain  at  Bake  Oven  Knob 40 

19.  Smooth  and  cultivated  crest  of  Kittatinny  Mountain  west  of  Bake  Oven 

Knob 41 

20.  Railroad  cutting  through  moraine  west  of  Kepner  saddle,  Schuylkill  Co.  42 

21.  Cobbles  from  gravelly  drift,  Balliet,  Carbon  Co 42 

22.  Glaciated  southern  outcrop  of  mammoth  bed,  Morea,  Schuylkill  Co 46 

23.  Glaciated  coal  outcrop  and  drift  cap,  Shamokin,  Northumberland  Co ....  53 

24.  Pocono  cobbles  and  trash  carried  from  Little   Mountain   (background) 

across  Mauch  Chunk  valley  at  Trevorton  and  left  on  Pottsville,  ibid. . .     53 

25.  Pocono  drift  from  Nescopeck  Mountain  on  Mauch  Chunk  extension  of 

McCauleys  Mountain,  at  Mountain  Grove,  Luzerne  Co 56 

26.  Pocono  and  Pottsville  conglomerate  on  Catskill  at  hill-top  north  of  Rush- 

town,  Northumberland  Co.     (Gravels  from  Susquehanna  River) 56 

27.  Pocono  cobbles  on  Hamilton  ridge  north  of  Shamokin  Creek  at  Deiblers, 

ibid.     (Showing  disappearance  of  Susquehanna  gravels.) 57 

28.  Gravels  from  Shamokin  Creek  on   ridge-top  near   cross-road  to  Paxinos, 

south  side  of  ridge,  ibid 57 

ix 


X  LIST  OF  ILLUSTRATIONS 

FIG.  PAGE 

29.  Bed  of  Middle  Creek  between  Adamsburg  and  Troxelville,  Snyder  Co. 

Drift  of  Oneida  to  Salina  on  Hamilton 59 

30.  Red  silt  including  Oneida  and  Martinsburg  on  Cambro-Ordovician  lime- 

stone, north  of  Huston,  Nittany  Valley,  Center  Co 62 

31.  Medina  cobble  and  quartz  pebble  from  drift  on  White  Deer  Mountain, 

south  of  Williamsport,  Lycoming  Co 63 

32.  Outwash  from  Lake  Lesley,  showing  gradual  slackening  of  current,  one- 

quarter  mile  south  of  Vail,  Blair  Co 66 

33.  Outwash  from  Lake  Lesley,  south  of  saddle,  at  East  Tyrone,  ibid 66 

34.  End  of  fan-cone  from  Antis  Gap,  near  Jersey  Shore,  Lycoming  Co 67 

35.  Detail  of  cutting  in  fan-cone  showing  rough  assortment  of  strata,  ibid ....  68 

36.  Section  of  fan-cone,  showing  drift  overlaid  by  unstratified  silt,  and  that 

by  slope-wash  from  Bald  Eagle  Mountain,  Mill  Hall  Gap,  Clinton  Co.  68 

37.  Cutting  through  Mill  Hall  fan-cone,  Clinton  Co 69 

38.  Cutting  through  fag-end  of  delta,  Emporium  Junction,  Cameron  Co 69 

39.  Orogenic  drift,  Sheffield,  Warren  Co 79 

40.  Lower  Indian  Hollow  sands,  east  side,  Warren  Co 84 

41.  Lower  Indian  Hollow  sands,  west  side,  ibid 84 

42.  Clay  lenticule  with  iceberg  burden,  in  Lower  Indian  Hollow  sands,  ibid.  85 

43.  Native  Copper  nugget,  clay  lenticule,  Lower  Indian  Hollow  sands,  ibid. ...  85 

44.  Upper  Indian  Hollow  sands,  ibid 86 

45.  Detail  of  plunge  and  flow  stratum,  Upper  Indian  Hollow  sands,  ibid 86 

46.  Clarendon  gravels  on  top  of  Upper  Indian  Hollow  Sands,  East  Warren,  ibid.  87 

47.  Early  Big  Bend  gravels,  Oakland  bar,  South  Warren,  ibid 91 

48.  Middle  and  Late  Big  Bend  gravels,  South  Warren  terrace-bar,  ibid 92 

49.  Clastics  from  South  Warren  terrace-bar,  showing  mixture  of  decayed  and 

fresh  pieces  of  same  formation 93 

50.  Crystallines  from  South  Warren  terrace-bar,  showing  mixture  of  decayed 

and  fresh  pieces.     Cobble  under  arrow  has  fresh  (white)  nucleus  exposed 

by  rolling 94 

51.  Western  end  of  South  Warren  terrace-bar,  showing  shaping  before  deposi- 

tion of  Leverett  clay 94 

52.  Sheer  walls  of  trench  through  "Old  Divide"  lined  and  capped  by  drift, 

Franklin,  Venango,  Co 97 

53.  Orogenic  drift  beneath  Leverett  clay,  Roystone,  Warren  Co 97 

54.  Iceberg  burden  in  Leverett  clay,  surface  at  Roystone,  ibid 98 

55.  Drift  overlaid  by  assorted  gravels,  Brandon,  Venango  Co 99 

56.  Thinness  of  Leverett  clay  over  assorted  gravels,  Kennerdell,  Venango  Co.  99 


INTRODUCTION 

CHAPTER  I 
TOPOGRAPHY 

Southeast  of  Alleghany  Mountain  Pennsylvania  topography  depends 
on  geological  outcrop.  The  ridges  are  Oneida,  Pocono  and  Pottsville; 
the  valleys,  trenched  into  Trenton,  Lower  Helderberg,  Salina  and  Mauch 
Chunk.  The  monotony  of  the  level  ridge  crests  is  due  to  the  Harrisburg 
peneplain.  The  Susquehanna,  Lehigh  and  Schuylkill  disregard  the  law 
that  the  drainage  should  follow  the  soft  outcrops,  and  break  through 
many  ridges  at  low-angled  gaps.  While  the  river  troughs  were  mainly 
trenched  preglacially,  their  finish  in  some  cases  is  due  to  glacial  torrents. 
Geological  outcrop  has  little  effect  on  topography  northwest  of  Alle- 
ghany Mountain.  While  the  preglacial  topography  north  of  the  Penn- 
sylvania plateau  has  been  modified,  and  in  places  submerged  beneath  a 
thick  drift-sheet,  that  south  of  the  same  approximates  closely  to  pre- 
glacial contours. 

The  dependence  of  topography  on  outcrop  is  illustrated  by  the  exten- 
sion of  the  Great  Valley  of  Pennsylvania  through  New  Jersey,  the  Hudson 
Valley,  and  Lake  Champlain  in  Cambro-Ordovician  measures.  Its  rock 
floor  is  at  times  far  below  ocean  level,  and  rises  above  it  150  feet  at  Smith's 
Basin,  N.  Y.;  514  feet  at  the  Wallkill-Rondout  saddle,  and  490  feet  at 
Toptoii,  Pa.,  and  thus  furnishes  the  only  low  level  approach  from  Canada 
to  Maryland.  By  this  there  was  an  escape  for  both  ice  and  flood  when 
the  Hudson  lobe  was  pocketed  at  Storm  King  Mountain.  The  average 
breadth  of  Hudson  Valley  between  the  500-foot  contours  is  16  miles; 
between  the  1000-foot,  32  miles.  South  of  Kingston  the  eastern  valley 
wall  approaches  the  river  till  at  Storm  King  Mountain  it  rises  1200  feet 
above  it.  Marlboro  Mountain,  opposite,  forms  an  equally  high  wall. 
The  southern  outlet  of  the  pocket  is  but  %  of  a  mile  broad  at  the  500-foot 
contour,  and  2  miles  at  1000  feet.  From  the  valley  trend  between  Hud- 
son and  Kingston  there  is  the  same  angular  turn  to  enter  the  pocket  as 
to  pass  southwestward  along  the  above  low  valley  to  Pennsylvania. 
This  valley  varies  from  6  to  2  miles  in  breadth  between  the  500-foot  con- 
tours, and  16  miles,  at  1000  feet.  The  closing  of  the  Storm  King  pocket 
sent  both  ice  and  flood  towards  Pennsylvania. 

1 


GLACJATION.    FIRST  PHASE 


In  what  follows  regarding  the  supposed  Erigan  system  of  Professor 
Spencer,  only  the  accepted  depths  ot  rock  floor  beneath  Lake  Ontario 
will  be  used.  The  flow  of  Keewatin  ice-cakes  eastward  probably  occurred 
before  the  Labrador  ice  fell  into  the  Central  New  York  depression.  There 
is  today  -a  channel  through  Mohawk  Valley  everywhere  below  500  feet 
above  ocean  level,  and  immediately  west  of  the  Mohawk  headwaters  the 
filled  condition  of  the  region  is  acknowledged.  It  is  evident  that  icebergs 
might  cause  clogging  which  would  pond  water  sufficiently  to  float  them, 
when  the  clogging  broke,  into  Hudson  River.  In  this  sense  the  Erigan 
drainage  into  the  Hudson  is  accepted,  without  claiming  a  definite  channel 
of  low  level. 

It  is  evident  that  the  St.  Lawrence  Valley  is  continued  westward  by 
a  deeper  rock  trough.  There  is  a  drop  of  700  feet  from  the  rock  shelf  of 
the  lake  to  the  trough  bottom.  The  Niagara  promontory  rises  900  feet 
above  this  valley  which  winds  about  it  via  Ancaster,  Canada.  The 
present  Wabash  watershed  is  800  feet  above  ocean  level.  The  rock 
floor  of  the  supposed  Erigan  trough  has  a  fall,  west  of  the  supposed  Gene- 
see  confluence  beneath  Lake  Ontario,  of  1.37  feet  per  mile.  If  there  were 
a  continuation  of  this  through  Mohawk  Valley  to  the  Hudson  rock  floor 
at  Storm  King  Mountain,  the  fall  would  be  1.42  feet  per  mile.  This  is 
merely  interesting,  in  view  of  the  evident  distribution  of  native  copper 
nuggets  (90  to  200  Ibs.)  in  drift  near  New  Haven,  and  in  small  nuggets 
and  shots  in  Eastern  Pennsylvania  drift. 

The  northern  border  of  St.  Lawrence  Valley  slopes  gently  to  the  river; 
the  southern  border  rises  sharply  therefrom.  The  trough  is  100  miles 
south  of  the  median  line  between  its  high  borders.  The  southern  border 
passes  along  the  Maine-Vermont  boundary  to  the  line  of  the  Green 
Mountains.  It  can  be  considered  as  passing  southward  along  them  to 
the  latitude  of  the  Catskills,  and  thence  westward  through  them  and 
along  the  Pennsylvania  plateau  crest.  The  Adirondack  uplift  is  con- 
sidered as  in  St.  Lawrence  Valley  and  surrounded  by  three  troughs  whose 
filled  surfaces  are  everywhere  below  500  feet  above  ocean  level.  The 
uplift  averages  3500  feet,  many  peaks  rising  above  4000,  and  Mount 
Marcy  to  5344.  At  500  feet  above  ocean  level  the  area  of  the  uplift  is 
over  18,000  square  miles;  at  2000  feet,  3,800  square  miles.  The  Black 
River  Valley  and  a  col  at  1000,  over  which  a  lobe  passed,  separate  this 
uplift  from  an  extension  whose  summits  rise  nearly  to  2000  feet  above 
ocean  level. 

The  Maine  boundary  rises  above  2000  feet.  This  continues  across 
the  northern  part  of  New  Hampshire  and  varies  on  either  side  of  this 
elevation  across  Vermont  till  the  Green  Mountain  extension  is  reached, 
where  it  rises  above  3000  feet,  and  sinks  thence  to  500  on  the  eastern  rim 
of  Lake  Champlain,  whose  valley  is  35  miles  broad  at  this  elevation,  and 
55  miles  at  1000  feet.  Its  water  level  is  slightly  below  100  feet  above 


TOPOGRAPHY  3 

ocean  level.  The  Green  Mountains  continue  the  high  border  at  an  eleva- 
tion above  2500  feet,  with  peaks  rising  to  4000.  The  Catskills  rise  to 
3500-4000  feet,  with  foot-hills  below  3000.  The  Pennsylvania  plateau 
extends  westward  at  2000-1600-2500  to  its  culmination  in  Potter  County, 
with  extensions  at  2200  through  McKean  and  Warren  counties  into 
Cattaraugus  and  Chatauqua  counties  (N.Y.)  at  the  same  elevation;  the 
Cattaraugus  extension  ending  in  the  Salamanca  promontory  which  drops 
abruptly  1170  feet  to  the  rock  floor  of  Allegheny  River  on  the  north  and 
west,  and  to  the  Tuna  Valley  on  the  east.  Beyond  this  river  the  plateau 
rises  as  a  high  wall  which  is  continued  northwestward  as  the  Niagara 
promontory,  above  described. 

The  rise  from  the  filled  Mohawk  trough  to  the  crest  of  the  Cat  skill 
foothills  is  1800  feet;  from  the  same  to  the  Pennsylania  plateau,  south  of 
the  Black  River  saddle,  1600;  from  the  Seneca-Cayuga  trough,  1200;  but 
only  600  thence  to  the  Stokesdale  saddle  into  Pine  Creek.  From  Erigan 
rock  floor  to  Potter  County  swamp,  via  Genesee  Valley  the  rise  is  3100 
feet.  The  profile  from  Erigan  rock  floor  southward  in  the  meridian 
through  Salamanca,  N.  Y.  places  the  250-foot  (above  ocean  level)  contour 
12  miles  south  of  the  trough  line  and  700  feet  above  it;  the  500-foot  con- 
tour is  22  miles;  the  1000-foot,  52  miles;  1500,  60  miles;  2000,  85  miles. 
The  crests  of  the  plateau  at  Salamanca  rise  to  2350,  and  thence  is  a  fall 
of  1320  feet  to  the  Allegheny  rock  floor.  A  second  profile  in  the  meridian, 
25  miles  west  of  the  former,  places  the  500-foot  contour  18  miles  south  of 
Erigan  trough;  1000,  44  miles;  1500,  47  miles;  1900,  65  miles.  A  third 
profile  between  Niagara  Falls  and  Warren,  Pa.,  places  the  500-foot  con- 
tour 24  miles  from  the  trough;  600  (top  of  Niagara  Falls  promontory), 
40  miles;  filled  Lake  Erie  floor,  52  miles;  1000-foot  contour,  72  miles; 
1500,  74;  approximate  rock  floor  of  buried  Allegheny  (900),  84;  2000-foot 
contour,  104;  2100  (crest  of  Quaker  Ridge),  114;  rock  floor  of  Conewango 
(1100),  118  miles.  These  show  a  ridge  40  miles  long  parallel  to  the  trend 
of  the  i^e-sheet  and  2400  feet  above  Erigan  trough.  The  Upper  Alle- 
gheny trough  lay  from  700  to  1000  feet  below  this  ridge,  and  south  of 
it  the  plateau  rose  abruptly  between  1000-1200  feet. 

Regional  striae  show  that  eastern  and  central  Pennsylvania  were  cov- 
ered by  lobes  from  the  main  trunk  which  passed  up  Erigan  Valley  to 
Illinois  on  a  trend  parallel  to  the  Allegheny  high  wall  and  trough.  It 
has  been  noted  that  Erigan  trough  was  100  miles  south  of  the  valley 
center.  This  produced  such  a  tendency  to  adjustment  of  the  mass  of 
the  ice-sheet  towards  the  trough  that  it  pressed  strongly  against  the 
southern  border,  and  induced  lobation  followed  by  united  movement  of 
the  whole  sheet  over  the  Pennsylvania  plateau,  while  Northwestern 
Pennsylvania  was  covered  by  the  spreading  of  the  southern  margin  of  the 
main  trunk. 

Applying  the  components  of  the  regional  striae  to  a  topographical 


4  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

map  we  find  that  definite  ice-streams  separated  from  the  main  St.  Law- 
rence trunk  at  three  branching  places.  The  first  is  Lake  St.  Peter,  in 
St.  Lawrence  River;  the  second,  100  miles  up  stream,  into  Black  River 
Valley;  the  third,  200  miles  up  stream  into  and  across  Erigan  Valley  at 
the  foot  of  Lake  Ontario,  where  there  was  a  drop  of  over  700  feet. 

From  Lake  St.  Peter  a  lobe  passed  up  St.  Francis  Valley,  across  the 
basin  of  Lake  Memphremagog,  over  the  Connecticut  watershed  (+2000) 
125  miles  distant,  with  passes  at  1120,  1246  and  1214,  and  through  Con- 
necticut Valley  to  Long  Island.  This  will  be  called  the  St.  Francis- 
Connecticut  River  Lobe,  or  No.  1,  and  will  not  be  further  considered  as  its 
only  influence  on  Pennsylvania  glaciation  was  the  reflex  of  its  own  resist- 
ance to  progress. 

A  second  lobe  passed  at  once  from  Lake  St.  Peter  into  the  broad 
mouth  of  Lake  Champlain  Valley.  This  narrows  to  5  and  3  miles  be- 
tween Whitehall  and  Stony  Point  at  the  500  foot  contour,  and  to  17  at 
1000  feet.  It  broadens  at  Fort  Ann  to  9  and  27  miles  at  these  elevations; 
to  1.6  and  25  miles  at  Smith's  Basin  saddle  (150).  Thence  to  Kingston, 
N.  Y.,  is  an  average  of  16  and  35  miles.  A  branch  separated  from  this 
at  Smith's  Basin,  and  two  more  at  Kingston.  This  separation  was  not 
immediate,  as  the  main  body  had  moved  on  its  way  for  centuries,  if  not 
millennia,  before  the  splits  left  the  region. 

At  Smith's  Basin  the  main  body  moved  down  Hudson  River  by  turn- 
ing to  the  left;  while  the  split  continued  in  the  Champlain  trend  to  the 
Mohawk  trough,  where  it  had  to  rise  1000  feet  to  pass  its  southern  wall, 
and  an  additional  900  feet  to  cross  the  Delaware  watershed.  It  could 
then  move  down  the  Delaware  Valley  to  the  eastern  boundary  of  Pennsyl- 
vania with  a  fall  of  500  feet  in  the  plateau  surface  and  of  1000  feet  to  the 
Delaware  trough.  Thence  there  was  a  long  and  easy  rise  over  broken 
country  to  the  crest  (2200-2500)  of  the  Moosic-Pocono  ridge,  which  was 
accompanied  by  a  contraction  in  breadth  to  42  miles  at  that  crest ;  to  20 
miles  at  the  headwaters  of  Lehigh  River;  to  12  miles  against  Susquehanna 
River.  Before  crossing  the  high  southern  bank  of  Mohawk  River  it 
spread  up  that  valley,  and  thus,  when  it  moved  southward  it  crossed 
also  the  headwaters  of  the  most  eastern  of  the  affluents  of  Susquehanna 
River.  There  are  passes  at  1550,  1500,  1410  and  1365;  the  two  former 
to  the  Delaware,  the  latter  to  the  Susquehanna.  This  lobe  will  be  called 
the  Champlain-Mohawk-Delaware-Pocono-Shamokin  Lobe,  or  No.  2.  It 
reached  the  Lehigh  headwaters  several  thousand  years  after  No.  3 
attained  its  farthest  bounds  and  had  passed  away. 

The  split  that  passed  directly  down  Hudson  Valley  was  pocketed  at 
Storm  King  Mountain  and  deflected  up  the  Wallkill-Rondout  valleys 
towards  Delaware  River  and  Pennsylvania,  along  a  trough  bottom  always 
below  520,  with  bordering  ridges  always  with  smooth  flanks  parallel  to 
the  glacial  trend,  so  that  additional  thickness  brought  only  commensurate 


TOPOGRAPHY  5 

bottom  drag.  The  accompanying  glacial  drainage  gave  a  water-worn 
fades  to  all  of  its  drift.  This  will  be  called  the  Champlain-Hudson- 
Delaware-Schuylkill  Lobe,  or  No.  3.  Its  drift  is  the  oldest  in  Pennsyl- 
vania, and  in  New  Jersey  is  called  "Jerseyan." 

When  the  pocketed  ice  at  Storm  King  Mountain  was  thick  enough  to 
cross  the  1200-foot  wall,  two  lobes  moved  therefrom.  One  passed  to  the 
Hudson  mouth,  the  other  to  New  Haven,  Conn.  The  Champlain- 
Hudson-Manhattan  Lobe,  or  No.  4,  does  not  enter  into  this  discussion. 
The  Champlain-Hudson-New  Haven  Lobe,  or  No.  5,  is  interesting  as  it 
carried  from  the  main  Hudson  trunk  masses  of  native  copper  up  to  90 
and  200  pounds,  while  No.  3  carried  shots  of  the  same  to  Eastern 
Pennsylvania. 

From  the  second  branching  place  a  lobe  passed  from  the  St.  Lawrence 
up  Black  River  Valley  140  miles  to  the  broad  saddle  at  1000  feet,  whence 
there  was  a  drop  of  over  1700  feet  to  the  rock  floor  of  the  Erigan-Mohawk 
trench  and  a  greater  rise  to  the  Susquehanna  watershed  with  cols  at 
1250,  1265  to  the  Unadilla,  and  at  1150  to  the  Chanango  affluents. 
These  cols,  by  piracy,  are  now  several  miles  north  of  the  watershed. 
West  of  the  Chenango  basin  a  2000-foot  ridge  separated  this  lobe  from 
No.  7,  which  also  drained  its  portion  of  the  160  miles  along  Central  New 
York  into  Susquehanna  River.  On  reaching  the  summit  of  the  Pennsyl- 
vania plateau  this  was  separated  from  No.  2  by  Moosic  Mountain,  whose 
high  wall  prevented  the  lobe  from  entering  Lackawanna  Valley.  It 
crossed  this  Pocono  wall  at  Pittston  Gap,  where  the  southern  side  is 
debased  to  1000,  or  1000  feet  below  the  crest  from  Moosic  Mountain 
southward.  This  wall  rises  again  to  1500  at  Plymouth  and  is  in  1500- 
1600  to  the  end  at  Huntington  Mountain,  where  the  great  moraine  was 
pocketed.  This  lobe  was  75  miles  broad  at  the  Pennsylvania  boundary; 
50  at  Wilkes-Barre;  55  at  Catawissa;  25  at  Selins  Grove;  and  10  at  the 
McClure  saddle.  It  will  be  called  the  St.  Lawrence-Black  River-Sus- 
quehanna  Lobe,  or  No.  6. 

From  the  third  branching  place  there  was  a  fall  into  the  Erigan  trough. 
If  this  were  partially  drained  into  Hudson  River  the  ponded  water  in 
it  was  below  800  feet  above  tide,  but  if  the  drainage  were  westward  the 
level  of  ponding  made  550  feet  of  depth  above  the  rock  shelf  along  the 
northern  shore  of  Lake  Ontario,  and  1300  over  the  Erigan  rock  floor — 
both  sufficient  to  cause  calving  of  bergs  from  the  glacial  margin  until 
the  valley  was  completely  clogged  and  the  trough  filled,  when  two  lobes 
separated.  That  to  the  east  moved  into  the  Cayuga-Seneca  lake  pocket, 
90  miles  broad  at  the  mouth  between  the  1000-foot  contours,  75  miles 
north  of  Pennsylvania,  but  30  broad  at  the  bottom,  20  miles  away,  with 
a  ridge  as  a  stopper  (1200)  and  passes,  to  the  east  (920);  to  the  west 
(990) — both  leading  into  the  Susquehanna  River.  The  Chenango  pass 
has  been  noted  above.  This  lobe  moved  southward  across  the  state 


6  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

boundary  and  then  opened  fan- wise:  the  left  margin  continuing  south- 
ward to  Muncy,  crossing  Bald  Eagle  Mountain,  and  reaching  almost, 
if  not  quite,  to  Penns  Valley;  the  right,  caught  in  the  broad  and  low 
troughs  of  the  plateau  top,  was  turned  westward  so  as  to  cross  Sinnema- 
honing  Creek  to  Medix  at  right  angles  to  the  trend  of  the  other  part. 
This  is  35  miles  broad  at  the  state  boundary;  60  at  Lock  Haven;  32  at 
Medix.  It  will  be  called  the  Ontario-Finger  Lake-Allegheny  Plateau 
Lobe,  or  No.  7.  i 

The  western  split  moved  up  Genesee  Valley,  crossed  its  high  western 
wall  and  the  Allegheny  trough  at  Vandalia,  N.  Y.,  reached  the  crest  of 
the  Pennsylvania  plateau  in  Potter  County  and  reached  Kane  and  the 
headwaters  of  Kinzua  Creek.  This  is  called  the  Ontario-Genesee- 
Sinnemahoning  Lobe,  or  No.  8. 

An  examination  of  the  outcrops  crossed  by  each  lobe  enables  us  to 
predict  the  possible  contents  of  the  drift  of  each.  The  location  of  tor- 
rents to  be  crossed  permits  the  possibility  of  the  loss  of  basal  burden. 
Each  lobe  thus  has  a  peculiar  drift-sheet,  approximating  to  the  regional 
outcrop  where  it  rests. 


CHAPTER  II 
THE  FIRST  PHASE 

The  initial  movement  of  the  first  glacier  was  of  necessity  burdenless 
and  over  an  aged,  soft  and  deep  surficial  mantle.  There  was  no  frontal 
moraine  during  its  progress,  as  this  depends  on  the  sum  of  continuity 
in  action,  supply  of  material  and  permanent  deposition.  The  bulk  of  a 
moraine  depends  more  on  the  last  than  on  the  power  of  the  ice-sheet  or 
its  percentage  of  burden.  The  moraine  of  Lewis  &  Wright  in  Cherry 
Valley,  the  drift  sheets  that  have  obliterated  preglacial  topography  in 
Western  New  York,  are  vast  because  they  were  dropped  against  ponded 
water  in  such  bulks  as  to  prevent  return  of  preglacial  lines  of  drainage. 
There  were  vast  amounts  of  burden  in  the  ice-sheet  as  it  lay  across 
Lycoming  Creek,  as  shown  by  the  Juniata  gravels;  but  there  is  no 
sign  of  a  moraine  at  the  crossing  or  for  some  distance  on  either  side.  The 
ponded  water  in  Erigan  Valley  has  been  noted.  This  was  pushed  over 
the  Pennsylvania  plateau  in  such  volumes  that  the  river  trenches  were 
unable  to  discharge  it,  and  it  swept  the  surface  along  lines  of  accumulation. 

Again,  the  initial  glacial  mass  was  of  the  highest  fluidity,  possessed  a 
low  front  (probably  300  feet  1  mile  from  the  face),  a  tendency  to  ready 
lobation,  free  passage  of  heat  rays  and  thus  great  bottom  depletion. 
This  last  produces  frequently  a  movement  of  vertical  ridge  outcrops 
indifferently  to  the  valleys  on  either  side,  whether  the  glacial  movement 


THE  FIRST  PHASE  7 

is  with  or  across  their  strike.  Its  effects  are  seen  also  in  the  "Rock 
Cities,"  which  can  hereafter  be  taken  as  evidences  of  an  ice-sheet.  The 
ridge-crests  of  Northwestern  Pennsylvania  are  residues  of  highly  jointed 
horizontal  strata.  The  stagnant  ice  molds  itself  over  these,  opens  the 
joints,  envelopes  the  separated  masses  and  moves  them  radially  from  the 
crest  to  various  distances,  leaving  them  with  strata  still  horizontal,  and 
joint-planes  vertical.  A  third  effect  of  bottom  depletion  is  the  uncover- 
ing of  crests  and  exposure  of  drift-caps  to  erosion  during  the  settlement 
of  ponded  water.  The  heavy  residues  at  high  levels  attest  the  former 
extension  to  those  levels  of  drift-sheets  now  buried  beneath  washes  in 
the  regional  troughs. 

Fluidity  also  imposed  a  rolling  motion  to  the  progress  of  the  ice- 
sheet,  with  a  maximum  retardation  of  basal  burden.  Mr.  Upham1  has 
considered  100  feet  per  year  as  a  maximum  rate  of  progress  for  basal 
ice,  and  one-half  to  one-third  of  the  same  as  the  probable  rate.  With  a 
main  trunk  400  miles  broad  and  so  slow  a  frontal  progress  it  is  evident 
that  there  would  be  little  or  no  motion  parallel  to  the  central  trend  along 
a  lateral  margin  spread  along  a  series  of  ridges  and  troughs  normal  to 
that  trend,  especially  if  that  margin  averaged  2500  feet  above  the  trough 
bottom.  The  boundary  of  such  a  margin  would  show  no  lobes,  but 
crenatures  varying  in  acuteness  and  extent  with  the  breadth  of  the  troughs 
and  the  rise  of  their  bottoms. 

The  rise  along  the  center  of  each  lobe  varies  with  fluidity,  nourish- 
ment and  resistance  to  progress.  Lateral  spreading  is  conditioned  upon 
an  excess  of  nourishment  over  depletion,  and  is  a  function  of  the  above 
three;  but  in  any  case  it  is  always  slower  and  more  intermittent  than 
frontal  progress.  In  the  case  of  Northwestern  Pennsylvania  it  was 
vastly  more  easy  to  move  from  the  Niagara  Falls  region  325  miles  along 
a  low  though  with  a  rise  of  200  feet,  than  to  move  at  right  angles  to  the 
central  motion  100  miles  with  a  rise  of  2000  feet. 

In  an  attempt  to  arrive  at  comparative  slopes  of  the  various  lobes 
there  was  used  the  rule  reported  by  Mr.  Lesley2  as  original  with  Pro- 
fessor Louis  Agassiz,  "That  no  glacier  can  cross  a  ridge  unless  its  thick- 
ness at  the  summit  of  the  ridge  is  at  least  one-half  the  height  of  the  ridge. >} 
Measurements  were  taken  along  the  line  of  motion  of  Lobe  No.  3  from 
the  Center  Valley  front  to  Port  Jervis,  N.  Y.,  and  thence  through  Mount 
Marcy,  the  highest  of  Adirondack  Mountains,  to  Lake  St.  Peter  in  St. 
Lawrence  River.  The  profile  of  the  line  was  compiled  from  the  state  and 
government  quadrangles.  Applying  the  above  rule  it  was  found  that 
to  cross  the  average  elevation  of  the  Adirondacks,  Kittatinny  and  South 
mountains,  the  surface  of  the  ice-sheet  would  rise  365  feet  above  South 

1  Upham,   Warren:  Fields  of  Outflow  of  the   North  American  Ice-sheet,   XII 
Internat.  Geol.  Cong.,  Toronto,  1913. 

2  Lesley,  J.  P.:  Letter  of  transmission,  vol.  z,  p.  14,  2d.,  Geol.  Surv.  Pa. 

2 


8  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

Mountain;  585  feet  above  Kittatinny  Mountain,  1850  feet  above  the 
Adirondack  average,  and  8000  feet  above  Lake  St.  Peter.  The  surface 
slopes  are: 

Center  Valley  to  South  Mountain,  126  feet  per  mile  (1°  23'  32+");  South  Moun- 
tain to  Kittatinny  Mountain,  43.5  feet  per  mile  (0°  22'  29+");  Kittatinny  Mountain 
through  Mount  Marcy,  15.5  feet  per  mile  (0°  11'  06+"). 

These  slopes  are  like  those  of.  modern  continental  ice-sheets.  Mount 
Marcy  and  Mount  Washington  of  the  White  Mountains  would  be  buried 
300  feet  below  this  surface,  while  Slide  Mountain  and  the  four  next 
in  height  of  the  Catskills  would  emerge  from  100  to  825  feet  above  it. 

In  the  following  calculations  the  results  are  interesting  rather  than 
conclusive.  At  best  they  are  comparative,  and  as  such  may  afford  a 
means  of  arriving  at  an  estimate  of  the  relative  times  of  arrival  of  the 
various  lobes  at  their  destination.  From  the  above  slopes  it  appears 
that  the  surface  of  the  theoretical  ice-sheet  is  about  800  feet  above  the 
elevation  of  the  frontal  base  at  a  point  1 1  miles  in  the  rear  of  the  latter. 
This  can  be  separated  into  a  rise  of  300  feet  for  the  first  mile  and  of  50 
feet  per  mile  for  the  following  ten.  Assuming  these  figures  for  the  fronts 
of  the  five  lobes  that  invaded  Pennsylvania  and  selecting  stations  on 
those  fronts,  the  relative  slopes  of  each  between  Lake  St.  Peter  and  points 
11  miles  back  from  each  front. can  be  found,  measuring  the  distances 
along  the  paths  followed  by  each  lobe.  These  distances  can  be  quite 
accurately  measured  along  Lobes  2,  3  and  6,  as  their  boundaries  are 
established  within  a  mile.  In  Nos.  7  and  8  it  is  only  possible  to  say  that 
the  ice-sheet  may  have  gone  farther  than  the  points  selected.  These  are : 

No.  2,  the  inside  of  the  Pocono  rim  where  Line  and  Little  mountains 
enclose  the  Mauch  Chunk  Valley  of  Zerbey  Run,  elevation  above  ocean 
level,  800  feet. 

No.  3,  Hamburg,  Berks  County,  against  Schuylkill  River,  elevation, 
550. 

No.  6,  McClure,  on  the  border  of  Snyder  and  Juniata  counties,  eleva- 
tion 640. 

No.  7,  Medix,  in  the  southeastern  corner  of  Cameron  County,  in  a 
narrow  river  trough  about  1150  with  the  plateau  average  above  it 
1600. 

No.  8,  Kane,  on  the  top  of  the  McKean  County  plateau,  2000,  with 
average  of  region  2100. 

No.  2.  Little  Mountain,  448  miles,  slope  14.64  feet  per  mile. 
No.  3.  Hamburg,  443  miles,  slope  15.41. 
No.  6.  McClure,  465  miles,  slope  14.44. 
No.  7.  Medix,  461  miles,  slope  12.44. 
No.  8.  Kane,  445  miles,  slope  11.74. 

The  distances  along  the  different  glacial  trends  agree  very  well, 
although  the  profiles  show  great  variations  in  elevations  overcome.  This 


THE  FIRST  PHASE  9 

raised  the  question  whether  this  boundary  line  of  the  Attenuated  Border 
could  not  be  taken  to  represent  the  curve  of  work  done  by  this  phase, 
and  the  great  moraine  to  represent  that  done  by  its  phase.  To  institute 
a  comparison,  lines  were  drawn  from  the  above  stations  along  the  lines 
of  glacial  flow  to  the  above  moraine,  and  other  stations  thus  found 
thereon,  with  their  elevation  above  ocean  level.  The  distances  between 
these  stations  were  measured,  the  above  average  slopes  calculated  back 
for  those  distances,  and  the  elevations  of  the  surfaces  of  the  above  lobes 
found  at  points  11  miles  back  from  the  second  series  of  stations.  The 
stations,  distances  from  boundary  to  moraine,  their  elevations  above 
ocean  level,  and  the  elevations  of  the  glacial  surface  of  each  lobe  are  as 
follows : 

No.  2.  Little  Mountain  (800)  to  Sandy  Run  (1000),  61  miles,  surface  2493. 

No.  3.  Hamburg  (550)  to  Nazareth  June.  (600),  48  miles,  surface  2089. 

No.  6.  McClure  (640)  to  Beachhaven  average  (900),  66  miles,  surface  2398. 

No.  7.  Medix  (1600)  to  Lloyd  (1600),  58  miles,  surface  3221. 

No.  8.  Kane  (2100)  to  Rose  Lake  (2055),  50  miles,  surface  3487. 

Subtracting  the  elevations  of  the  second  series  of  stations  from  the 
elevations  of  the  lobes  behind  them  we  find  the  rise  in  11  miles  for  each 
to  be:  No.  2,  1493  feet;  No.  3,  1489;  No.  6,  1493;  No.  7,  1621;  No.  8, 
1432  feet;  average,  1520.  This  last  figure  agrees  well  with  modern 
types  of  continental  ice-sheets  in  rising  500  feet  per  mile  for  the  first 
mile,  and  100  per  mile  for  the  next  10  miles.  When  this  is  considered 
with  the  parallelism  between  the  above  boundary  and  the  great  moraine 
it  seems  plausible  to  suggest  that  they  are  representatives  of  the  first  and 
mature  phases  of  the  same  ice-sheet,  especially  as  their  drift-sheets  are 
identical,  as  far  as  elastics  are  concerned,  and  the  crystallines  of  the 
moraine  are  absent  from  the  outer  border  because  of  the  retardation  of 
the  basal  ice. 

Taking  up  the  second  part  of  the  calculation  the  question  will  be 
asked  if  it  be  possible  to  arrive  at  the  relative  times  of  arrival  of  these 
lobes  at  their  boundary,  using  Professor  Agassiz's  rule  for  thickness,  and 
Mr.  Upham's  for  speed.  The  former  is  definite,  the  latter  relative,  and 
the  periods  will  be  measured  in  years  of  100  feet  progress.  As  an  example, 
Lobes  2  and  3  separated  theoretically  at  Smith's  Basin,  N.  Y.,  though 
the  barrier  between  them  was  not  visible  on  the  surface  till  the  rise  along 
Hudson  River  to  Catskill  Mountains  was  reached.  There  was  no  obsta- 
cle before  No.  3  until  within  25  miles  of  Delaware  River,  where  the 
Wallkill-Rondout  watershed  to  the  latter  rose  to  514  with  easy  slope  from 
Hudson  River.  No.  2,  on  the  contrary,  must  rise  1000  feet  within  a  mile 
or  two  to  cross  the  southern  bank  of  Mohawk  River,  and  1900  feet  to 
cross  the  Hudson-Delaware  watershed.  On  reaching  the  Delaware 
River  boundary  of  Pennsylvania  there  was  a  farther  rise  of  1300  feet  to 
the  Moosic-Pocono  plateau. 


10  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

With  the  above  rule  for  thickness  the  ice-sheet  must  have  stood  900 
feet  above  the  Delaware  watershed  and  have  had  a  surface  elevation  of 
2700  feet  above  ocean  level  at  a  point  84  miles  south  of  Smith's  Basin. 
This  would  indicate  a  corresponding  elevation  of  No.  3,  84  miles  from  the 
same;  but  as  this  would  be  in  the  Hudson  trough,  it  would  indicate  a 
thickness  of  2700  feet  for  that  lobe.  With  its  average  slope  of  15.41  feet 
per  mile,  its  front  should  be  many  miles  to  the  south.  The  average  eleva- 
tion of  the  Wallkill-Rondout  trough  is  300  between  the  Hudson  and  its 
watershed,  and  this  average  continues  into  Pennsylvania.  Adding  this 
elevation  to  the  assumed  800  feet  of  rise  11  miles  back  from  the  front 
of  the  First  Phase  lobe,  we  can  find  the  distance  from  the  point  84  miles 
south  of  Smith's  Basin  to  where  the  glacial  surface  would  be  1100  feet 
above  ocean  level  with  a  slope  of  15.41  feet  per  mile,  or  104  miles,  which 
would  bring  the  front  11  miles  farther,  or  across  Delaware  River  and  half 
way  between  Belvidere  and  Martin's  Creek.  From  the  watershed  to 
the  Delaware  River  boundary  of  Pennsylvania  No.  2  would  move  down 
a  slope  for  60  miles.  Supposing  both  lobes  moved  with  equal  speed, 
which  is  favoring  No.  2,  the  front  of  No.  3  would  have  advanced  60  miles 
farther,  or  63  miles  from  Belvidere,  and  8  miles  beyond  its  farthest  exten- 
sion. This  would  indicate  that  No.  3  ended  its  advance  before  No.  2 
touched  Pennsylvania.  The  distance  from  Smith's  Basin  to  Hamburg  is 
240  miles  along  the  Cambro-Ordovician  trough.  At  100  feet  per  annum 
No.  3  would  cover  the  distance  in  12,672  years,  and  No.. 2  would  require 
about  13,000  years  to  reach  the  eastern  Pennsylvania  boundary.  It 
would  remain  near  there  till  its  front  thickened  from  300  feet  frontal 
elevation  to  an  elevation  above  ocean  level  sufficient  to  send  a  thickness 
of  (one-half  of  1300  above)  650  feet  over  the  Moosic-Pocono  plateau,  32 
miles  distant  from  the  river  crossing.  With  the  slope  of  14.64  feet  per 
mile  this  would  indicate  an  increase  of  2500  feet  above  the  original  300, 
and  an  uninterrupted  progress  along  a  plain  of  180  miles,  at  14.64  feet 
per  mile.  Its  rest  along  the  Delaware  River  till  it  moved  across  the 
Moosic-Pocono  ridge  was  about  9500  years,  and  its  progress  about  16  feet 
per  year.  It  would  reach  the  headwaters  of  Lehigh  River  long  after 
No.  3  had  reached  its  bounds  and  had  been  more  or  less  completely  re- 
moved. This  accords  with  the  consensus  of  opinion  that  the  drift  of 
No.  3,  called  "  Jersey  an"  in  New  Jersey,  is  the  oldest  in  the  region.  It 
also  accords  with  the  conditions  in  the  Lehigh  Valley,  where  the  earliest 
efforts  of  No.  2  over  the  headwaters  of  Lehigh  River  come  after  the  last 
of  the  deposits  from  No.  3  have  been  laid,  as  will  be  described  later. 
Owing  to  lack  of  accurate  data  along  the  profiles  of  the  other  lobes  no 
further  comparisons  will  be  made.  In  other  ways  we  are  able  to  find 
overlaps  and  coalescences  of  neighboring  borders  without  decision  as  to 
relative  times  of  arrival.  It  is  probable  that  the  youngest  is  the  most 
westerly,  and  that  the  spreading  of  the  margin  of  the  main  trunk  over 
Northwestern  Pennsylvania  was  near  the  ending  of  the  advance. 


CHAPTER  III 
THE  FLUVIAL  FORCES 

From  the  dimensions  of  trenched  cols  we  know  that  streams  of  great 
power  were  at  work,  but  from  the  sizes  and  shapes  of  the  assorted  pieces 
in  the  deposits  we  know  that  their  velocities  were  considerable  only  when 
confined  to  the  trenches.  Otherwise  they  swept  slowly  across  broad  areas 
and  left  abundant  deposits  where  ponding  or  slackened  currents  obtained. 
The  presence  in  the  drift  of  large  rock-masses,  or  cobbles  and  boulders 
above  the  average  indicates  ice-carriage  in  the  mass  or  by  bergs  and 
cakes. 

The  average  small  sizes  of  the  assorted  pieces  in  the  deposits  makes 
the  current  velocities  that  carried  or  dropped  them  pertinent  to  this 
inquiry.  Fine  clay  is  worked  by  a  stream  of  3  inches  per  second;  fine 
sand,  6;  coarse  sand,  8;  fine  gravel,  12;  1-inch  gravel  (round,  24;  angular, 
36).  If  1-inch  round  and  angular  mixtures  are  fed  into  a  24-inch  stream, 
at  the  end  of  the  operation  the  bottom  would  show  angular  only.  This 
is  why  in  slabby  regions,  in  spite  of  abundant  glacial  gravel  fed  to  streams, 
the  bottoms  are  purely  slabby.  Where  Kettle  Creek  meets  Lake  Lesley 
we  find  round  gravel — otherwise  its  bottom  is  slabby,  as  are  the  other 
Sinnemahoning  affluents  that  drain  the  glacier.  Oil  Creek  bottom  above 
the  great  moraine  is  also  slabby. 

The  water-worn  character  of  the  drift  in  general  shows  that  the  First 
Phase  was  a  fluvial  one,  and  especially  in  Northwestern  Pennsylvania 
where  the  southern  margin  of  the  main  trunk  spread  upwards  to  the 
Pennsylvania  plateau.  Before  the  level  of  ponded  water  reached  the  col 
at  the  head  of  the  submerged  valley  the  combined  floods  of  regional  and 
glacial  discharge  escaped  along  the  marginal  canyon  trenched  between 
the  glacial  margin  and  the  regional  slope,  and  as  the  ice-sheet  moved 
upwards  this  canyon  and  its  floods  were  pushed  higher  and  higher  along 
the  slopes.  The  area  of  the  canyon  would  thus  vary  greatly  as  it  crossed 
flooded  valleys  or  was  trenched  through  the  intervening  ridge-crests, 
and  where  occasion  offered  there  would  be  deposition  of  coarser  sorts, 
which  now  are  called  " high-level  channels,"  "high  beaches,"  as  they 
cling  to  the  sides  of  valleys  above  present  water  level. 

The  rivers  on  the  southern  sides  of  the  cols  were  trenched  by  the 
floods  forced  over  the  cols,  and  thus  a  large  part  of  the  trenching  they 
show  today  was  performed  before  the  actual  advent  of  the  ice  to  their 
basins,  though  the  agents  may  have  been  more  or  less  glacial.  The 
Susquehanna,  Schuylkill  and  Lehigh  are  good  examples,  and  all  three 
flow  in  places  over  glacial  fillings  50  feet  deep. 

11 


12  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

There  is  a  difference  in  the  efficiency  of  the  glacial  dam  whether  the 
ice-sheet  moves  up  or  across  a  valley.  In  the  latter  case  there  is  a  leak- 
age owing  to  the  constant  adjustment  of  the  ice  along  its  periphery  to 
the  inequalities  of  the  surface  over  which  it  passes,  and  this  leakage,  with 
proper  head  and  volume  may  become  sufficiently  erosive  to  remove  the 
basal  ice,  especially  as  it  would  require,  according  to  Mr.  Upham  (op.  cit.) 
from  1  to  3  years  for  that  layer  to  cross  a  stream  100  feet  broad.  The 
only  efficient  dam  is  where  the  margin  of  an  ice-sheet  spreads  upwards  so 
as  to  pond  all  the  drainage  of  a  region  and  to  discharge  it  along  a  marginal 
canyon.  The  flood  in  this  latter  erodes  the  regional  slope  and  especially 
the  ridges  across  which  the  canyon  is  located.  The  local  material  thus 
removed  is  dropped  with  the  glacial  debris  against  the  ice-margin  where 
it  crosses  the  submerged  valley,  and  thus  stops  all  leakage  by  forming 
a  deep  deposit  over  which  the  ice  moves  upwards.  The  result  is  to  fill, 
and  even  obliterate  old  channels  and  valleys,  by  hundreds  of  feet  of  drift, 
as  in  Western  New  York,  which  remain  undisturbed  because  the  trench- 
ing of  Big  Bend  and  other  cols  from  450  to  1000  feet  furnished  a  perma- 
nent escape  for  the  regional  drainage  southward.  Drive-pipe  records 
attest  to  the  great  depth  of  filling  in  the  above  valleys. 

The  carriage  of  drift  to  high  levels  by  ice-cakes  borne  on  the  crest  of 
long  and  high  waves,  incident  to  the  bursting  of  ephemeral  ice-dams 
formed  by  icebergs  and  cakes  in  the  " narrows"  of  streams,  has  been 
described  for  Juniata  River  by  the  writer  (cf.  preface  note  D,  pp.  182— 
183).  The  three  great  areas  of  ponded  water  in  the  state  have  been 
mentioned:  Lake  Packer  (preface  note  B,  pi.  ix);  Lake  Lesley  (ibid.,  D, 
p.  184);  and  Lake  Allegheny  (ibid.,  F).  The  first  two  names  remain, 
with  due  regards  to  Professor  Wright  (ibid.,  G,  p.  153)  for  suggesting 
another  name  for  the  first.  The  last  name  has  been  preempted  for  other 
things,  and  a  further  study  of  the  region  makes  it  impossible  to  comprise 
the  various  areas  of  ponded  water — now  connected,  now  separate — under 
one  name.  They  can  be  described  under  three  aggregates.  The  most 
northerly  is  connected  with  the  old  Upper  Allegheny  Basin,  and  for  a 
long  time  it  included  the  second,  which  covered  the  Warren- Clarendon 
area.  The  third  covered  the  old  Middle  Allegheny  Basin.  For  the 
first  the  name  Lake  Wright  is  suggested,  as  Professor  G.  Frederick  Wright 
was  the  first  to  claim  a  continuity  of  the  Indian  Hollow  (East  Warren) 
deposits.  In  addition  he  gave  to  the  writer  25  years  ago,  the  impetus 
that  induced  him  to  examine  the  Attenuated  Border.  The  second  much 
smaller  body  is  called  the  Conewango  Slack  Water.  For  the  third  the 
name  Lake  Leverett  is  suggested,  as  the  monograph  (preface  note,  A)  of 
Mr.  F.  Leverett  has  been  followed  by  the  writer  in  the  arrangement  of 
the  various  preglacial  Allegheny  drainages,  and  has  left  little  undone  in 
marking  the  boundary  of  the  Attenuated  Border  there.  These  will  be 
described  later. 


DRIFT  OF  THE  FIRST  PHASE  13 

The  action  of  a  reversed  stream  discharging  over  the  col  at  the  valley 
head  is  interesting.  The  current  starts  from  the  old  valley  mouth,  or 
wherever  the  ice-margin  crosses,  and  moves  to  the  upper  wedge-end,  acquir- 
ing velocity  from  two  causes :  the  narrowing  cross-section  and  the  dis- 
charge of  affluents.  The  old  projections,  bars,  deltas,  have  been  sculp- 
tured to  favor  movement  down  stream,  and  the  reversed  current  moves 
against  and  is  deflected  by  them.  The  head-on  discharge  of  each  affluent 
is  against  a  gradually  swifter  flood.  There  is  no  such  quiet  flow  as  in  a 
torrent  of  equal  head  moving  down  stream;  there  is  a  struggle  between 
warring  forces  which  must  tear  away  all  projections  and  fill  all  holes 
where  slackness  prevails.  Only  when  this  is  done  behind  shoulders  of 
hills,  or  on  the  inside  of  bends,  does  anything  like  smoothness  of  flow 
obtain.  Today  we  find  these  fillings  of  holes  far  above  present  water 
level,  and  we  must  not  mistake  them  for  complete  valley  fillings.  The 
great  classical  gravel  deposits  of  East  Warren,  Brandon  and  Kennerdell 
are  foreset  deposits  in  holes  of  reversed  currents. 

The  col  at  the  head  of  a  reversed  current  is  trenched  by  material 
taken  immediately  from  its  vicinity.  The  current  on  starting  from  the 
ice-sheet  is  at  its  slowest  speed,  and  drops  everything  of  bulk  against 
that  sheet.  As  it  acquires  velocity  it  picks  up  burden  of  the  lighter  and 
smaller  sorts,  and  this  becomes  heavier  with  increase  in  velocity  till, 
at  the  wedge-end  of  the  valley  it  tears  away  the  entrance  to  the  col  trench 
and  cuts  down  the  sides  and  floor  with  this  coarse  material,  which  is 
immediately  dropped  as  soon  as  the  trench  is  past  and  the  current  slackens 
in  the  broader  valley  beyond.  When  the  trench  is  sunk  to  the  level  of 
the  old  valley  mouth  there  is  a  channeling  through  the  old  valley  floor. 
This  depth  of  trenching  seldom  happens  and  there  is  generally  a  portion 
of  the  old  filling  remaining  as  a  floor  for  the  stream.  Infrequently,  and 
where  a  plunging  scour  obtained,  the  old  rock  floor  at  the  valley  head 
for  a  considerable  distance  from  the  col  is  cleared  from  its  drift  filling. 
After  this  flow  subsides  an  area  of  shallow  ponding  remains  that  is 
filled  with  late  foreset  beds. 


CHAPTER  IV 
I     DRIFT  OF  THE  FIRST  PHASE 

This  covers  in  Pennsylvania  a  strip  300  miles  long  and  (measured  in 
the  meridian)  43  miles  broad  east  of  McKean  County,  but  (measured 
on  N.  45°  W.)  less  than  one-half  that  distance  west  of  the  same.  The 
drift  is  uniform  only  in  its  fluvial  appearance  in  and  near  lines  of  drain- 
age, and  its  angularity  and  local  character  beyond  their  influence.  The 


14  PENNSYLVANIA  GLAC1ATION.    FIRST  PHASE 

change  in  criteria  is  shown  by  considering,  "  What  is  drift?"  and  "  When 
did  it  age?" 

What  is  Drift? 

The  forces  that  induced  glaciation  were  not  localized  and  confined 
to  the  Labrador  origin,  but  formed  snow  caps,  if  not  local  glaciers,  on 
neighboring  crests;  whose  ablation  caused  abnormal  washing  of  ridge 
slopes,  erosion  of  troughs,  burdening  of  floods  with  material  from  the 
old  surficial  mantle  that  was  rolled  proportionally  with  stream  power  and 
distance  carried,  and  deposition  of  the  burden  to  form  the  oxidized  and 
incompletely  rolled  formations  that  will  be  called  below  Orogenic.  This 
is  not  true  drift,  though  connected  with  glaciation. 

True  drift  approximates  to  the  local  outcrops  because  of: 

First. — The  retardation  of  basal  burden. 

Second. — The  very  frequent  movement  of  the  ice-sheet  along  the  valleys,  and 
thus  along  the  strikes  of  the  measures. 

Third. — The  more  or  less  complete  removal  of  the  basal  burden,  with  the  basal 
ice,  during  the  crossing  of  a  torrential  stream  (cf.  p.  10). 

Fourth. — The  massing  of  basal  ice  against  a  steep  rise,  the  shear  developed,  and 
the  passage  of  the  top  clear  ice  to  and  over  the  crest  (preface  note,  D,  p.  182). 

Fifth. — The  washing  of  basal  ice  through  crevasses,  and  the  dropping  of  the 
burden  where  crevasses  always  form — on  the  far  side  of  every  sharp  angle  in  the  sur- 
face. Susquehanna  and  Oil  Creek  gravels  will  be  noted  below. 

By  the  first,  the  frontal  ice  of  the  First  Phase  was  clean  when  it 
reached  its  farthest  boundary.  During  the  first  year  the  moraine 
accumulations  were  from  the  30  to  100  feet  next  it.  Unless  the  out- 
crop of  a  different  formation  came  to  the  surface  within  a  mile  the 
accumulations  of  from  50  to  100  years  would  be  like  those  of  the  front. 
Thus,  at  Bethlehem  for  1200  years  nothing  but  Cambro-Ordovician 
limestone  would  be  brought  by  the  ice-sheet.  The  materials  of  a  moraine 
would  thus  resemble  the  overturned  soil  of  a  thick  mantle,  such  as  exists 
in  Saucon  Valley  south  of  the  rock  trains  between  Friedensville  and 
Bingen. 

This  is  true  drift  even  if  nothing  foreign  is  found.  In  the  countless 
instances  where  the  surficial  mantle  seemed  to  be  untouched  and  of 
ordinary  thickness  close  observation  might  find  one  or  more  erratics  in 
a  mile  of  cutting,  or  a  square  mile  of  area.  Mr.  Barrell  styled  the  search 
for  foreigners,  "  Hunting  needles  in  haystacks/7  as  one  erratic  was  fre- 
quently the  sole  find  after  days  of  search.  The  " Needles"  are  usually 
rolled  pieces  among  angulars,  red  strays  on  white  outcrops,  and  vice 
versa,  crystallines  amid  elastics  or  coal,  and  other  marked  rocks  carried 
above  their  outcrops.  The  bulk  of  the  formation  is  as  surely  drift  without 
as  with  these  foreigners.  As  examples,  Figure  42  shows  rocks  from  bergs 
dropping  in  a  clay  lenticule  (East  Warren).  Figure  43  is  a  nugget  of 
native  copper  therefrom.  Figure  8,  a  Lower  Helderberg  cobble  in  gneiss 


DRIFT  OF  THE  FIRST  PHASE  15 

debris.  Figure  9,  some  trap  cobbles  (right  foreground)  in  the  same. 
The  two  latter  from  South  Bethlehem. 

When  did  the  Drift  Age? 

After  25  years  of  study  it  seems  that  the  aged  appearance  is  inherent 
and  not  acquired.  Figures  1  (Saucon  Valley),  2  (Lehigh  Valley),  3 
(Upper  Juniata  Valley)  show  the  contrast  between  the  deep  red  of  the 
surficial  mantle  and  the  color  of  the  fresh  and  polished  cobbles.  The 
time  elapsed  since  drift  deposition  is  measured  by  the  freshest  part. 

Rustiness  and  decomposition  are  more  rapid  over  the  soft  porous 
Mississippian-Pennsylvanian  areas  of  Western  Pennsylvania  than  over 
the  denser  ones  of  the  Anthracite  Basins,  and  vastly  more  rapid  than 
over  those  with  outcrops  below  the  Mauch  Chunk — excepting  rocks 


FIG.  1. — Brownish-red  silt  including  quartzite  cobbles,  Bingen,   Northampton  Co. 

cemented  by  calcite — because  of  the  presence  of  pyrite  in  the  coal 
measures.  This,  when  moistened,  becomes  efflorescent  and  soluble, 
and  when  exposed  to  the  sun  and  air  breaks  into  limonite  and  sulphuric 
acid.  The  former  stains,  the  latter  decays  whatever  they  touch.  Such 
decay  is  especially  rapid  in  the  black  bisilicates  of  crystalline  rocks. 
Drift-sheets  near  such  solutions  are  suspicious  when  stained  or  decayed. 
Where  an  overwash  drift-sheet  is  underlaid  by  a  limonite  hardpan  we 
can  be  certain  that  the  latter  was  not  only  leached  from  the  preglacial 
rustiness  of  the  gravel,  but  was  laid  and  hardened  in  its  present  posi- 
tion before  the  water  in  which  the  deposit  was  dropped  had  been  drained 
away.  The  rustiness  of  the  Pottsville  conglomerate  pebbles  is  found  in 
the  drift  sheet  and  in  the  solid  rock  along  a  quarry  face,  and  seems  to 
have  been  inherent  to  the  pebbles  before  solidification. 


16  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


FIG.  2. — Cutting  through  bar,  West  Bethlehem  gravels,  Northampton  Heights. 


FIG.  3. — Outwash  of  Lake  Lesley,  Dix  col,  Blair  Co. 


DRIFT  OF  THE  FIRST  PHASE  17 

The  decay  in  a  rock  floor  may  also  have  been  preglacial.  Tn  the 
fall  of  1913  Dr.  Miller  of  Lehigh  University  showed  the  writer  the  pre- 
glacially  decayed  limestone  floor  of  the  East  Allentown  gravel  workings. 
The  boulders  (dropped  from  icebergs)  fell  through  the  200  feet  of  water 
and  " splashed"  into  the  soft  surface  so  as  to  raise  a  rim  about  them  of  an 
inch  in  height.  Sporadic  patches  of  denser  rock  came  to  the  surface. 
At  the  time  of  deposition  a  man's  footprints  would  have  been  depressed 
in  the  soft  mud. 

Deforestation  reduced  the  ferric  salts  in  the  surficial  silts  from  red, 
yellow  and  brown  to  blue,  by  intermingling  vegetable  matter.  Leach- 
ing extracted  the  color  and  left  whitish,  mottled  and  streaked  beds. 
Thus  the  blued  clay  is  of  the  same  age  of  deposition  as  the  red  orogenic 
clays  of  the  same  region  which  are  found,  now  above,  now  beneath  the 
blue.  Color  here  is  no  criterion  of  age. 

The  extent  of  a  possible  scour  in  a  region  as  a  criterion  of  age  must 
be  accepted  only  when  actual  " fag-ends"  of  complete  valley  fillings 
remain.  Deposits  found  where  subsequent  scour  would  not  operate 
must  be  considered  with  the  query  whether  the  present  direction  of 
the  stream  which  is  supposed  to  have  removed  the  bulk  of  the  deposit 
is  that  of  the  stream  by  which  the  deposit  was  made,  as  depositions  in 
deep  water  through  which  a  current  passed  could  have  been  dropped 
originally  where  scour  did  not  operate  while  those  portions  of  the  valley 
where  it  was  active  would  be  swept  clean.  One  sure  proof  of  the  latter 
condition  is  the  shaping  of  the  deposit  to  its  present  state  before  the 
sinking  of  the  ponded  water,  the  thinning  out  of  strata  as  they  came  near 
the  line  of  scour,  and  the  capping  by  clay,  sand  or  silt  under  conditions 
which  show  that  it  is  not  a  slope-wash.  For  example,  the  bars  between 
Warren  and  Foxburg  are  not  remnants,  as  they  fulfil  all  the  conditions 
of  those  dropped  where  scour  did  not  operate,  as  do  those  in  the  Susque- 
hanna  and  Lehigh  regions.  There  has  thus  been  no  erosion  of  either 
rock  floor  or  of  complete  valley  fillings  in  any  of  the  main  valleys  of  the 
state.  They  may  exist  here  and  there  in  some  of  the  small  side  runs;  but 
the  erosion  from  the  latter  took  place  as  the  level  of  ponded  water  fell, 
because  the  main  channel  was  open  and  the  sands,  becoming  quick, 
ran  out,  as  they  did  from  beneath  the  gravel  at  Stoneham. 

Lastly,  the  mining  of  slate  and  coal  from  beneath  porous  drift  should 
make  us  adopt  new  criteria  regarding  rock  decay,  and  assume  that  the 
fresh  and  undecayed  rocks  in  drift  of  aged  appearance  indicate  that  the 
aged  portion  is  to  be  assigned  to  the  preglacial  surficial  mantle  unless 
exposed  to  solutions  from  pyrite.  But,  as  these  fresher  rocks  are  erratics 
and  "needles,"  it  is  safe  to  conclude  that,  unless  we  have  disposed  of  the 
preglacial  surficial  mantle  elsewhere,  the  aged  and  decayed  drift  deposits 
we  encounter  along  the  Attenuated  Border,  and  even  in  such  mature 
deposits  as  are  found  in  Vermont,  must  be  assigned  to  that  mantle,  as 


18  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

it  has  been  shown  along  that  border  that  there  has  not  been  sufficient 
time  since  the  First  Phase  for  rocks  to  reach  the  state  of  decay  of  these 
old  appearing  drifts  by  ordinary  agencies. 

The  length  of  the  foregoing  introduction  is  necessary  to  an  under- 
standing of  the  standpoint  of  the  writer  in  the  following  description  of 
the  deposits  of  the  Attenuated  Border,  and  the  controversial  statements 
were  necessary.  It  remains  to  consider  the  drift-sheets  of  the  various 
lobes,  the  conditions  of  deposition,  the  outcrops  crossed,  the  possible 
composition.  The  presence  of  very  aged  and  very  fresh  pieces  of  an 
extreme  foreigner  in  the  same  drift  can  be  accounted  for  by  glacial  and 
berg  carriage.  While  the  former  might  indicate  millennia  of  transit, 
the  latter  would  be  accomplished  in  as  many  hours,  and  would  be  de- 
livered either  fresh  or  as  decayed  as  the  piece  of  red  granite  found  at 
1500  on  the  hill  south  of  Franklin,  with  angular  quarry  face,  but 
pulverulent. 

In  the  following  scheme  no  attempt  is  made  to  form  a  stratigraphic 
column  to  include  all  the  lobes.  The  only  exception  is  where  the  Packer 
Clay,  the  first  of  the  deposits  of  No.  2,  is  found  capping  the  last  of 
those  from  No.  3.  The  rocks  of  the  drift-sheets  of  the  lobes  are  so 
different  from  one  another,  and  of  each  sheet  so  variant  in  different 
parts  of  its  area,  that  it  seemed  well  to  name  each  of  them  as  it  is  found 
in  Pennsylvania. 

SCHEME  SUGGESTED  FOR  PENNSYLVANIA  DRIFT-SHEETS 

PREGLACIAL 

Orogenic. — For  definition  see  p.  14.  Always  approximates  closely  to  the  local 
outcrop. 

GLACIAL 

DRIFT  OF  THE  FIRST  PHASE 

Lobe  No.  3. — Great  Valley  Drift 

Synchronous  with  "Jerseyan"  in  New  Jersey,  and  a  continuation  of  it.  The 
expected  elastics  come  from  the  lowest  New  York  outcrops  up  to  the  Pocono.  Crys- 
tallines from  Canada,  the  Adirondacks  and  Green  Mountains.  Native  copper 
also.  The  earliest  drift  in  Pennsylvania.  Crystallines  found  only  near  Delaware 
River  and  the  South  Mountain  (gneiss)  uplift. 

Lobe  No.  2. — Broad  Mountain  Drift 

Expected  crystallines  as  above.  Clastics  as  above  and  including  the  coal  measures. 
Foreign  rocks  very  rare.  Subsequent  in  time  to  No.  3. 

Lobe  No.  6. — Susquehanna  Drift 

Crystallines  and  elastics  to  be  expected,  as  in  No.  2.  No  crystallines  found. 
Lewistown  limestone  and  Salina  shale  abundant  in  main  valley.  Coalesced  with  No. 
2  and  No.  7.  Rolled  gravel  abundant  south  of  Susquehanna  River. 

Lobe  No.  7.— Plateau  Drift 

Clastics  from  Ordovician  to  the  coal  measures.  No  crystallines  found.  North 
of  Susquehanna  River  mainly  Mississippian-Pennsylvanian;  south  of  Bald  Eagle 
Mountain,  Ordovician  to  Clinton.  Rolled  pieces  abundant  south  of  Susquehanna 
River.  Overwash  into  and  through  Juniata  River. 

Lobe  No.  8. — Highland  Drift 


DRIFT  OF  THE  FIRST  PHASE  19 

Clastics  from  Chemung  to  the  coal  measures.  No  crystallines  found.  Rolled 
pieces  numerous.  Outwash  stratified. 

Southern  Lateral  Margin  of  Main  Trunk — Fluviatile  Drift 

The  possible  rock-forms  run  from  New  York  and  Canadian  crystallines  through 
the  sedimentary  measures  up  to  the  coal.  Local  rocks  and  in  immediate  vicinity 
Chemung  to  coal  measures.  Angular  and  local  drift  on  ridges;  rolled  and  crystalline 
drift  in  valleys.  Iceberg  action  abundant.  Deposition  in  ponded  water  voluminous; 
ridge-drift  thin. 

In  accordance  with  the  above  scheme  it  is  possible  to  eliminate  the 
outwashes  from  the  great  moraine  and  to  arrange  the  varieties  of  drift 
from  No.  3,  in  the  extreme  east,  and  from  the  Lateral  Margin  of  the 
Main  Trunk,  in  the  extreme  west;  as  in  both  regions  sections  which 
contain  all  the  formations  noted  below  can  be  studied  to  the  rock  floor. 
In  the  extreme  east  alone  is  there  a  true  overlap  of  formations  from 
different  lobes.  When  sections  through  the  deposits  in  the  center  of 
the  state  afford  chance  for  study  it  is  probable  that  similar  overlaps 
may  be  found.  The  names  which  follow  are  suggested  as  affording  places 
where  the  various  deposits  can  be  best  studied,  and  where  they  are 

typical. 

EASTERN  PENNSYLVANIA 

OROGENIC  BEDS— PREGLACIAL 

Sporadic  red,  yellow  and  brown  angular  accumulations  of  local  rocks  lying  against 
the  rock  floor.  Noted  along  the  flanks  of  South  Mountain  in  cellar  holes.  Matrix 
of  silt  with  inclusions  of  rough-surfaced  and  decayed  pieces  of  gneiss.  Resembles 
the  final  slope-wash  that  overlies  the  drift,  but  is  not  so  sandy,  and  the  rocks  are  more 
decayed.  Overlain  by  drift,  of  similar  color,  but  with  different  burden. 

GLACIAL 

Lobe  No.  3.— Great  Valley  Drift 

EARLY  GREAT  VALLEY  PERIOD.     LAND-LAID  DRIFT 

The  following  varieties  have  been  found,  and  are  described  without  attaching 
significance  to  the  order  of  arrangement.  They  indicate  the  local  and  sporadic 
character  of  the  varieties  which  were  accumulated  at  the  same  time,  though  in  no 
instance  fcave  they  been  found  to  shade  into  one  another. 

A.  Matrix  of  Damourite  paste  that  balls  like  clay,  greenish-gray,  carrying  flakes 
and  small  slabs  of  the  mineral,  usually  angular  and  rubbed  slightly  on  an  edge;  also 
rolled  and  polished  pebbles  of  quartzite  and  sandstone — the  latter  white  and  with 
pitted  egg-shell  surface  (see  preface  note  B,  plate  11  and  context).     Found  only  at 
small  area  along  the  eastern  side  of  Rauch's  Pit,  West  Bethlehem,  against  decayed 
and   glaciated    Ordovician   limestone.     2   feet   thick.     Underlying    West  Bethlehem 
gravels. 

B.  Unassorted  gravelly  drift  of  rolled  pebbles  of  white  sandstone,  quartzite,  and 
other  light  colored  elastics,  60  feet  thick,  of  limited  area  at  Mountainville  on  saddle 
between  Saucon  and  Great  Valleys,  resting  on  quartzite. 

C.  Matrix  of  silt,  red,  yellow,  brown,  carrying  the  local  outcrop,  but  firmer 
than  it.     Pieces  angular  at  South  Bethlehem.     Ten  feet  thick  at  Bethlehem  and 
contains  limestone  also.     Found  on  the  above  saddle,  and  there  more  sandy.     Shown 
in  Figure  8  on  col  back  of  South  Bethlehem,  gneiss  sand  and  a  few  foreign  inclusions. 
On  the  crest  of  Kittatinny  Mountain  a  slightly  larger  percentage  of  rolled  pieces 


20  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

are  found.  Over  the  slate  belt  the  matrix  is  more  or  less  decayed  slate.  At  Shoe- 
makersville  the  slate  flakes  are  firm  and  include  polished  sandstone  boulders  (Figure 
12).  In  many  places  it  seems  to  be  the  old  surficial  mantle  overturned  (Bethlehem, 
Center  Valley). 

D.  Lateral  moraine.     Found  along  the  northern  flank  of  South  Mountain  west  of 
Alburtis,  full  of  cobbles,  mainly  of  quartzite.     Carried  on  to  the  limestone  valley 
floor  by  settlement  of  stagnant  ice  towards  valley  trough. 

E.  Skeletonized  rock  trains  (moraines?).     One  series  extends  from  Klinesville 
northeast  to  Jacksonville  and  thence  at  an  angle  to  Lowhill,  south  of  Kittatinny 
Mountain.     Three  lines  extend  across  Saucon  Valley  between  Friedensville  and 
Bingen,  the  largest  75  feet  broad  and  10  high. 

LATE  GREAT  VALLEY  PERIOD 

WATER-LAID  DRIFT.     GLACIAL  OUTWASH,     DRUMLINS.     KAMES 

These  formations  are  found  below  500  feet  above  ocean  level,  as  the  regional 
ponding  never  extended  above  that  elevation.  They  are  thus  distinguished  from  the 
postglacial  slope  washes  which  are  found  at  all  elevations.  Instead  of  this  capping 
they  are  covered  with  an  iceberg  clay  (see  Packer  Clay  below). 

As  they  are  all  connected  with  the  ablation  of  the  stagnant  ice-sheet  this  name  is 
suggested  for  their  divisions. 

EARLY  ABLATION  DIVISION.     Strong  Currents 

Formation  of  narrow  channel  in  the  ice  between  Lehigh  Gap  and  Easton,  via 
Slatington  and  Bethlehem.  Scour  of  rock  floor  and  removal  of  most  of  the  drift- 
sheet.  Current  too  strong  for  deposition  of  coarse  gravel.  Icebergs  abundant,  and 
deposits  only  of  boulders  and  masses  from  their  collision  or  melting.  It  is  probable 
that  the  second  part  of  this  division  is  much  later  than  the  first,  and  was  laid  after  a 
broader  channel  had  been  cleared  and  an  extension  made  over  the  northern  edge  of 
Fountain  Hill. 

A.  Boulders  sporadically  distributed  against  the  decayed  rock  floor  in  the  East 
Allentown  gravel  working.  Usually  average  6  inches  diameter,  but  are  found  up 
to  12  to  14  inches.  Frequently  the  deposit  is  so  thick  (2  feet)  that  it  is  left  unworked. 
The  stratified  gravel  is  removed  by  machinery  to  its  top,  and  the  remainder  of  the 
sands  cleared  away  by  hand. 

B.  Masses  of  Kittatinny  rocks  against  the  decayed  limestone  floor  on  northern 
edge  of  Fountain  Hill,  in  sizes  up  to  11  X  4  X  4  feet.  At  least  10  feet  thick,  as 
bottom  was  not  reached  in  excavation.  Evidently  an  eddy  deposit,  as  it  is  localized 
to  a  small  area. 

LATE  ABLATION  DIVISION.     Medium  and  Variable  Currents 

No  increase  in  the  volume  of  the  stream,  but  enlargement  of  channel  between  the 
ice-walls,  and  thus  reduction  of  velocity.  The  gradual  broadening  of  the  channel 
brought  more  rapid  ablation,  so  that  the  velocity  was  not  greatly  diminished  during 
this  division  till  the  area  below  500  feet  above  ocean  level  was  cleared  of  ice.  In- 
frequent larger  pieces  from  iceberg  carriage. 

A.  West  Bethlehem  Gravels. — Assorted  sands  and  fine  gravels  with  few  pebbles  and 
infrequent  cobbles  laid  in  wavy  strata  which  thin  out  towards  the  east,  where  they 
came  within  the  influence  of  the  Monocacy  flow  from  the  north.    At  this  eastern  end 
the  strata  are  in  foreset  beds  (see  Figure  14).    Thickness  10  to  12  feet;  at  Twelfth 
Avenue,  West  Bethlehem,  120  feet — both  parts  of  a  bar  4  miles  long  with  top  +160 
feet  above  the  rock  floor.    Another  long  and  thick  bar  at  Northampton  Heights  is 
cut  through  by  the  Philadelphia  &  Reading  Railroad  in  passing  about  the  east  end  of 
South   Mountain.     Numerous  Kames  are  parallel  to  Lehigh  River  on  the  inside  of 
curves  in  which  are  rock  masses  weighing  tons  (iceberg  carriage). 

B.  Lehigh  Quicksands. — Clean  quicksands  without  inclusions  ending  on  top  in  the 


DRIFT  OF  THE  FIRST  PHASE  21 

most  impalpable  rock  meal,  fresh  color,  up  to  5  feet  thick.  Absent  at  Rauch's  Pit, 
owing  to  proximity  to  the  Monocacy  current.  The  above  thickness  at  Twelfth 
Avenue,  West  Bethlehem.  The  Emaus  drumlin  belongs  here,  laid  in  conical  strata 
from  a  center,  as  on  a  convex  buddle,  composed  of  fine  material  that  could  be  carried 
by  a  strong  wind,  mainly  fine  sand. 

C.  Current  of  Clear  Water.  No  Deposition. — End  of  the  Removal  of  bergs  from 
the  cleared  periphery  of  the  stagnant  ice.  No  icebergs  or  ice-cakes.  Slight  sculptur- 
ing of  the  east  end  of  the  gravels  in  Rauch's  Pit.  See  Figure  14  for  the  difference  in 
dip  of  the  stratified  gravels  and  their  junction  plane  with  the  overlying  clay.  This 
is  possibly  due  to  the  beginning  of  the  trenching  of  the  Monocacy  gorge  through  the 
limestone  roll  of  Bethlehem  hill. 

Lobe  No.  2. — Broad  Mountain  Drift 

EARLY  BROAD  MOUNTAIN  OUTWASH.     ICEBERG  CLAY 

This  is  found  only  in  the  portion  of  Lehigh  Valley  south  of  Mauch  Chunk,  and 
it  attains  its  greatest  thickness  along  South  Mountain.  The  structure  of  the  deposit 
indicates  a  levitated  silt  unmixed  with  vegetable  material,  and  retaining  the  dark  red 
of  the  surficial  mantle  from  which  it  was  derived.  It  carries  sporadically  abundant 
large  angular  pieces  dropped  from  icebergs  at  all  angles  into  the  deposit.  These 
extend  beyond  the  series  found  in  the  drift  of  No.  3  lobe,  and  include  micaceous  sand- 
stones of  the  coal,  and  partly  decomposed  pieces  of  anthracite.  It  is  therefore  derived 
from  the  Lehigh  headwaters,  and  the  large  pieces  are  brought  by  ice-cakes.  This 
indicates  the  arrival  of  No.  2  over  the  Lehigh  headwaters.  The  absolute  quietness 
of  the  flow  is  shown  by  the  impalpable  grains  of  the  clay,  which  is  levitated  from  the 
coarse  sands,  and  over  large  areas  is  clean  and  worked  for  brick-making.  There  was 
thus  no  great  increase  in  the  flow  of  Lehigh  River  from  the  advent  of  No.  2.  The  level 
of  ponded  water  is  about  500  feet  above  ocean  level  south  of  Kittatinny  Mountain, 
and  is  slightly  above  this  north  of  the  Lehigh  Gap.  The  ponding  is  evidently  due  to 
clogging  of  the  narrows  of  Delaware  River,  south  of  Riegelsville  by  bergs,  as  No.  2 
was  crossing  that  stream  on  its  way  over  the  Moosic-Pocono  ridge.  The  ice-cakes 
were  small,  and  the  inclusions  in  the  clay  of  moderate  size.  The  latter  are  usually 
rough,  and  came  from  the  decayed  outcrops  of  the  Upper  Lehigh  Basin. 

A.  Packer  Clay. — The  name  is  given  to  this  deposit  in  Glacial  Lake  Packer.     An 
iceberg  clay,  deep  red  in  color,  found  generally  below  500  feet  above  ocean  level.     Laid 
in  current  of  less  than  3  inches  per  second.     Thickness  2  feet  near  main  current,  28 
to  30  at  Twelfth  Avenue,  West  Bethlehem. 

BROAD  MOUNTAIN  GRAVELS.     OUTWASH 

B.  Upper   West  Philadelphia  Gravels. — These  resemble  the  flood-plain  gravels 
along  Little  Schuylkill  and  Schuylkill  Rivers.     The  lower  gravels  seem  to  belong  to 
the  Early  Great  Valley  Period  of  No.  3. 

NOTE. — There  is  no  other  division  thus  far  made  of  this  drift,  or  of  the  deposits 
of  the  other  lobes.  No  arrangement  will  be  made  here;  but  the  variations  will  be 
noted  in  the  descriptions  of  the  various  areas. 


NORTHWESTERN  PENNSYLVANIA 

OROGENIC  BEDS— PREGLACIAL 

See  definition  at  beginning  of  scheme.  As  slope  washes  and  valley  fillings. 
Thickness  from  10  to  125  feet.  Abundant  outside  of  the  glacial  border,  and  form 
extensive  beds  below  1200  feet  above  ocean  level,  along  streams  away  from  the  glacial 
outwashes. 


22  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

FLUVIATILE  DRIFT 

EARLY  FLUVIATILE.     OUTWASHES 

Strictly  speaking  the  earliest  of  these  came  from  the  action  of  No.  8  in  moving  up 
Genesee  Valley,  but  its  distribution  and  deposition  was  in  water  ponded  by  the 
southern  margin  of  the  main  trunk,  and  thus  the  formation  falls  under  the  above 
heading.  Deposited  from  streams  with  moderate  velocities.  The  beds  are  found 
against  the  rock  floor,  on  quicksands,  and  on  orogenic  beds.  The  same  kinds  of  de- 
posits are  found  interstratified  with  later  deposits,  as  the  agencies  that  formed  the 
materials  continued  till  the  end  of  the  glacial  advance. 

A.  Conewango  Clay. — An  unstratified,  sticky,  blued  clay  including  wood  frag- 
ments and  logs.    Found  along  the  discharge  from  Glacial  Lake  Genesee  via  Cuba  pass, 
Olean,  Salamanca,  Kennedy  and  Warren  towards  Barnesville.     Varies  in  thickness 
from  a  few  inches  at  Sheffield  to  over  200  feet.     Not  distributed  generally  over  the 
ponded  water  of  the  region.     Free  from  sand  and  inclusions. 

B.  Lower  Indian  Hollow  Sands. — Very  fine  interstratified  quicksands  and  fine 
sands  with  sandy  clay  lenticules.     The  sands  are  perfectly  assorted  and  without 
inclusions;  the  lenticules  contain  sands,  gravel  (angular),  pebbles  and  cobbles  dropped 
from  icebergs.     Studied  at  a  section  in  the  deposit  at  Indian  Hollow,  opposite  East 
Warren.     See  Figures  40,  41,  42,  43.     Thickness  there  60  feet,  dip  17°  to  the  south, 
foreset  bedding  thinning  out  down  the  dip.     Also  at  State  Line,   125  feet  thick. 
Also  at  Glade  and  Clarendon.     At  the  latter  place  40  feet  thick  for  this  and  the  next 
bed. 

C.  Stronger   Current.     No   Deposition. — The   current   quickened  sufficiently    to 
level  these  fine  sands  along  a  horizontal  plane  1315  feet  above  ocean  level. 

D.  Upper  Indian  Hollow  Sands. — Horizontally  stratified  coarse  sands  and  fine 
gravels  laid  in  horizontal  wavy  strata.     Fresh   appearance,   20  feet  thick.     One 
stratum  shows  plunge-and-flow  bedding.     Upper  surface  at  1336  above  ocean  level. 
Figures  44,  45.     Found  also  at  Glade  and  Clarendon. 

MIDDLE  FLUVIATILE 

The  lateral  margin  of  the  Main  Trunk  had  arrived  sufficiently  near  to  drop  its 
burden  on  the  spots  where  we  now  find  the  deposits  of  this  period.  They  are  thus 
laid  above  or  below  the  level  of  ponded  water  of  the  region.  But,  as  the  ice-sheet 
covered  its  northern  portion  before  it  reached  that  to  the  south  it  follows  that  the 
northern  drifts  and  outwashes  are  the  older  of  the  two  series,  but  without  superposi- 
tion upon  those  most  southern. 

LAND-LAID  DRIFT.     All  above  the  level  of  ponded  water  of  the  region. 

A.  Garland  Type. — On  hill-top  near  Garland.     Red  silt  including  angular  slabs 
of  the  local  outcrop.     One  crystalline  pebble  found  imbedded  in  the  mixture. 

B.  Kane  Type. — On  surface  of  plateau  and  along  Kinzua  Valley  sides.     Sand  in- 
cluding flakes  of  local  rocks,  angular  cobbles,  boulders  and  masses  of  sandstone 
up  to  12  X  12  X  4  feet.     Found  on  top  of  stratified  sands,  discoidal  gravel  and  clay. 

C.  Brandon  Type. — A  thin  wash  like  the  last,  sandy,  carrying  rounded  boulders  of 
sandstone  up  to  3  feet  in  diameter. 

D.  Foxburg  Type. — Like  Garland  Type.     Red  silt  carrying  rolled  crystalline  peb- 
bles and  cobbles.     Coal  fragments  carried  up  hill  above  the  outcrop. 

OUTWASH.     In  ponded  water. 

A.  Clarendon  Gravels. — Stony  gravel  in  wavy  foreset  bedding  varying  from  nearly 
horizontal  to  17°.  Varies  in  proportion  of  foreign  and  rolled  pieces.  Thickness  40 
feet.  Forms  the  moraine  at  this  place  measuring  over  1000  feet  along  a  cross-section. 
Found  also  at  Indian  Hollow  on  top  of  the  same  stratified  sands  extending  over  2200 
along  the  hill  slope  (100  feet  vertical).  Also  formerly  filled  the  basin  of  Hook's  River. 
Preglacially  rusted.  Limonite  hardpan  beneath  from  leaching  of  rust.  Fig.  46. 


DRIFT  OF  THE  FIRST  PHASE  23 

LATE  FLUVIATILE 

This  belongs  to  the  interval  between  the  ending  of  the  glacial  activity  and  the 
clearing  of  the  troughs  of  the  stagnant  ice  through  which  the  torrential  discharges 
could  escape.  This  is  the  epoch  of  the  beginning  of  the  trenching  of  Big  Bend  col. 
The  following  beds  were  laid  in  the  channels  cleared  through  the  stagnant  ice,  and 
thus  bear  to  this  portion  of  the  ice-sheet  the  same  relation  that  the  West  Bethlehem 
gravels  do  to  No.  3,  with  the  exception  that  the  materials  are  derived  mainly  from 
fillings  of  the  neighboring  basins  of  the  Clarendon  gravel  epoch.  They  are  redistrib- 
uted gravels  with  admixtures  of  local  pieces. 

WATER-LAID  DRIFT.     In  ponded  water. 

A.  Early  Big  Bend  Gravels. — Similar  in  appearance  to  the  Clarendon  gravels,  and 
swept  from  Dutchman's  Run,  Hook's  River,  Glade  and  vicinity.     Laid  in  dipping 
foreset  bedding  in  a  long  bar  extending  on  to  the  plain  at  South  Warren.     Oakland 
Cemetery  is  located  on  this.     Figure  47. 

B.  Middle  Big  Bend  Gravels. — Later  than  the  above.     Big  Bend  col  trenched  to 
enable  the  scour  to  sweep  out  the  rilling  of  the  Salamanca-Kinzua  portion  of  the 
present  Allegheny  River  channel.     Varies  considerably  in  crystallines  and  elastics 
from  the  last.     Forms  the  long  and  lower  bar  at  South  Warren  used  as  a  railroad  gravel 
pit.     Figures  48,  49,  50,  51.     There  were  three  divisions  of  this  sedimentation: 

Ba.  Coarse  gravel  and  pebbles  with  little  sand.  Pebbles  3  inches  in  diameter. 
Wavy  horizontal  strata,  extends  from  5  feet  above  car  track  to  unknown  depth. 

Bb.  Lenticular  sandy  streaks  lapping  over  like  shingling,  nearly  horizontal,  3 
to  4  feet  thick. 

Be.  Small  assorted  gravel  in  foreset  bedding,  dip  17°.     Thickness  10  to  12  feet. 

Bd.  Increase  in  current  so  as  to  level  horizontally  the  top  of  the  above  deposit. 
No  deposition. 

C.  Late  Big  Bend  Gravels. — Unassorted  gravels  with  abundant  boulders  (iceberg) 
in  foreset  bedding  forming  the  top  of   the   gravels   in   the   South    Warren   bar. 
Thickness  18  to  20  feet. 

Ca.  Increase  in  current  so  as  to  level  the  top  of  this  bed.     No  deposition. 

D.  Leverett  Boulder  Clay. — A  sandy  clay  with  abundant  boulders  of  larger  sizes 
than  in  the  uppermost  gravels.     Figure  48  shows  the  shelf  on  top  of  these  gravels  from 
which  this  clay  has  been  removed.     The  long  pile  of  boulders  on  this  side  of  the  cars 
is  taken  mainly  from  this.     8  feet  thick  here.     Varies  elsewhere  from  2  to  8,  and  in 
the  south  is  more  sandy  and  quite  free  from  iceberg  burden. 

NOTE. — Mr.  Charles  Butts  (Warren  Folio)  places  all  these  formations  about  War- 
ren in  the  "Kansan  or  pre-Kansan"  period.  There  is  thus  an  agreement  as  to  their 
age. 


THE  ATTENUATED  BORDER 

CHAPTER  V 
GREAT  VALLEY  DRIFT.     LOBE  NO.  3 

The  Champlain-Hudson-Delaware-Schuylkill  Lobe  moved  with  the 
glacial  drainage  down  a  valley  with  low  trough  trenched  into  Cambro- 
Ordovician  rocks.  The  highest  outcrop  along  its  borders  is  Pocono. 
Abundant  rolled  pieces  met  it  at  the  Delaware  River  crossing.  Incorpo- 
rated in  it  were  icebergs  from  Professor  Spencer's  Laurentian  and  Erigan 
rivers  which  brought  native  copper  and  crystallines.  This  was  the 
earliest  of  the  lobes  to  reach  Pennsylvania,  and  thus  it  left  the  oldest 
drift.  The  area  covered  by  No.  3  is  thus  divided : 


FIG.  4. — Reddish  silt  including  local  and  foreign  gneiss,  Riegelsville,  Nhn.  Co. 

Durham  and  Reading  Hills. 

The  Great  Valley. 

Glacial  Lake  Packer  and  the  Glacial  History. 

Kittatinny  Mountain. 

The  Lower  Helderberg  and  Marcellus  Valleys. 

The  first  three  divisions  have  been  treated  before  (see  preface  note,  B  and  C), 
and  only  a  brief  treatment  of  the  first  two  will  be  attempted.  For  topography  see 
quadrangles  of  Easton,  Allentown,  Slatington,  Reading  and  Hamburg.  For  the 
geology  see  the  4-sheet  map  of  the  last  state  survey. 

25 


26 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


Durham  and  Reading  Hills — The  South  Mountain. — Figure  4 
shows  the  drift-sheet  at  Riegelsville,  west  of  the  town  and  above 
the  Delaware  gravels.  It  is  from  10  to  15  feet  thick,  and  carries 
boulders  of  dark  hornblende  gneiss  up  to  2j/£  feet  in  diameter.  Over 
Rattlesnake  Hill  it  carries  cobbles  of  local  gneiss  9  inches  in  diameter. 
Native  copper  has  been  frequently  reported  east  of  Saucon  Valley. 

Saucon  Valley. — Figure  1  shows  the  drift-sheet  in  a  railroad  cutting 
south  of  Bingen  station.  Figure  5  is  where  Saucon  Greek  cuts  through 
the  southernmost  of  the  rock  trains  southwest  of  Bingen.  The  mass  is 
of  gneiss  from  the  crest  of  South  Mountain.  The  woods  indicate  that 
the  tract  is  too  stony  for  cultivation.  Figure  6  is  on  the  side  of  a  rail- 


FIG.  5. — Moraine  traversed  by  Saucon  Creek,  near  Bingen,  Nhn.  Co. 

road  cutting  Y±  mile  south  of  Center  Valley.  The  red  silt  includes 
quartzite,  Triassic  shale,  angular  gneiss.  This  is  below  the  level  of 
glacial  Lake  Packer.  Figure  7  shows  a  mass  of  Oriskany  sandstone  on 
the  side  of  the  Philadelphia  Road  at  Friedensville.  Note  the  rough 
quarry-face  and  the  casts  of  spirifer  arenosus.  The  piece  was  brought 
over  Kittatinny  Mountain,  across  the  Great  Valley  and  over  South 
Mountain.  The  other  rocks  are  mainly  from  Kittatinny  Mountain. 

The  southern  part  of  this  valley  should  be  carefully  examined,  as  it 
seems  as  if  the  old  surficial  mantle  has  been  stirred  by  an  ice-sheet  that 
brought  nothing  to  the  mixture.  This  is  seen  1  mile  south  of  Coopers- 
burg,  and  between  this  place  and  Limeport,  above  the  level  of  glacial 
Lake  Packer  (500).  The  boundary  of  the  Attenuated  Border  can  be 
drawn  from  Monroe,  on  Delaware  River,  so  as  to  include  Durham  Valley 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3 


27 


and  the  cove  of  Saucon  Valley  about  Coopersburg,  thence  to  the  rise 
west  of  Friedensville  and  along  the  mountain  flank  south  of  Mountain- 


FIG.  6. — Brownish-red  silt  including  quartzite,  gneiss,  Triassic  red  shale,  railroad 
cutting  south  of  Center  Valley,  Nhn.  Co. 


FIG.  7. — Mass  of  Oriskany  sandstone  showing  casts  of  Spirifer  arenosus,  Friedensville, 
Nhn.  Co.,  part  of  moraine  across  Saucon  Valley. 

ville,  where  60  feet  of  gravel  (Early  Great  Valley  B,  see  scheme)  are 
found.     Figure  8  shows  a  Lower  Helderberg  pebble  (under  the  arrow- 


28 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


point)  in  a  drift  sheet  of  gneiss  sand  on  the  col  of  South  Mountain 
between  the  last  named  place  and  South  Bethlehem.     Figure  9  is  angular 


FIG.  8. — Lower  Helderberg  pebble  (beneath  arrow)  in  gneiss  sand  on  col  of  South 
Mountain  southwest  of  South  Bethlehem,  Nhn.  Co. 


FIG.  9. — Pile  of  trap  cobbles  taken  from  drift  of  gneiss  and  quartzite,  near  crest  of 
South  Mountain,  South  Bethlehem,  Nhn.  Co. 

local  drift  of  great  thickness  on  South  Mountain  worked  for  sand.     The 
pile  of  cobbles  in  the  right  foreground  contains  rounded  pieces  of  trap. 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3 


29 


West  of  Mountain ville  the  ice-sheet  did  not  cross  South  Mountain, 
but  its  lateral  moraine  gradually  accumulated  until  west  of  Topton  it 
was  composed  of  abundant  cobbles  of  gneiss  and  quartzite  intermixed 
with  gravel  and  angular  local  pieces.  This  was  somewhat  incorporated 
into  the  margin  of  the  ice  which,  during  the  ablation  and  settlement 
towards  the  valley  trough,  settled  away  from  the  mountain  and  on 
to  the  limestone  plain,  so  that  some  of  this  drift  is  separated  from 
the  wash  down  the  slope  by  a  slight  ridge  parallel  to  the  mountain.  This 
is  seen  west  of  Topton.  The  drift  from  Alburtis  westward  varies  in 
thickness  along  the  mountain  flank  from  20  to  120  feet,  and  many 
cuttings  through  it  were  made  by  the  railroad  between  Allentown  and 
Reading. 

As  the  trend  of  South  Mountain  changes  to  the  south  at  Blandon,  this 
drift  accumulation  leaves  its  flank  and  grows  thin  as  it  nears  the 
Schuylkill  River  and  the  front  of  the  ice-sheet. 

The  Great  Valley. — The  peculiarities  of  its  drainage  on  either  side  of 
Lehigh  River  have  been  described,  with  a  map  (see  preface  note  B).  The 
new  features  to  which  attention  should  be  called  are  the  Emaus  drumlin 


FIG.  10. — Merchantable  slate  beneath  .drift,  Siegfried's,  Northampton  Co. 

which  Professor  Benj.  L.  Miller  discovered  in  his  work  about  Allentown. 
This  has  been  noted  in  the  glacial  scheme  (Late  Ablation,  B,  Late  Great 
Valley  Out  wash).  It  stands  so  entirely  away  from  the  flank  of  the 
mountain  that  it  can  not  be  a  slope  wash.  The  materials  are  fine  enough 
to  have  been  blown  upon  the  glacial  surface  by  winds.  It  was  formed  by 
a  slight  trickle  down  a  crevasse.  There  is  nothing  up  to  J4  mcn  diameter 
in  the  body  of  fine  silty  sand.  The  foreigners  are  specks  of  quartz 


30  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

veinstuff  from  the  slate  and  of  chert  from  the  limestone.  It  is  capped  by 
the  usual  dark  red  silty  Packer  Clay  carrying  the  usual  iceberg  burden  of 
pebbles  and  cobbles  of  considerable  size.  The  unstratified  dark  clay 
cap  is  entirely  different  from  the  body  of  stratified  fine  sand  which  slopes 
everywhere  from  a  central  axis  as  if  laid  on  a  convex  buddle. 

The  quarrying  of  merchantable  slate  immediately  beneath  drift  has 
been  mentioned  in  previous  publications.  Figure  10  is  from  a  quarry  1 
mile  west  of  Siegfrieds  Station.  The  solidity  of  the  slate  under  the  drift 
is  well  shown.  This  indicates  that  from  60  to  80  feet  of  surficial  decayed 
mantle  have  been  removed,  as  that  amount  is  usually  " mucked"  from 
an  unglaciated  slate  body  before  merchantable  slate  is  reached. 

Attention  is  called  to  the  extraordinary  distance  that  the  500-foot 
contour  (see  Hamburg  quadrangle)  has  been  trenched  into  the  northern 
slope  of  Kittatinny  Mountain  by  the  headwaters  of  Ontelaunee  Creek — 
a  greater  distance  than  anywhere  else  in  the  vicinity.  This  will  be 
again  considered  when  we  describe  this  mountain.  The  drift-sheet  of 
this  region  is  monotonous,  as  the  ice-sheet  moved  parallel  to  the  strikes 
of  the  outcrops,  so  that  slate  was  picked  up  by  the  ice  and  dropped  on 
slate:  the  Hudson  sandy  beds  on  similar  outcrops:  limestone  on  lime- 
stone. There  is  little  other  than  the  infrequent  erratics  from  other  for- 
mations to  tell  that  this  is  drift  over  the  valley  floor.  Near  the  streams 
are  bodies  of  partly  rolled  gravel,  rounded  cobbles  and  boulders  that 
appear  to  have  been  developed  by  spheroidal  weathering.  It  is  only  by 
finding  unmistakable  drift  beds  farther  west  that  we  appreciate  that  this 
portion  has  been  covered  by  the  ice.  Apparently,  it  has  not  been  at  all 
glaciated,  in  the  old  acceptance  of  the  term. 

On  the  third  crest  of  the  Maiden  Creek-Schuylkill  watershed,  3J^ 
miles  east  of  Hamburg  is  a  drift-sheet  of  unknown  thickness,  consisting 
of  slate  flakes  and  slabs  including  Oneida  and  Medina  gravel,  cobbles  and 
boulders,  and  overlaid  by  5  feet  of  reddish  sandy  silt  including  rusty 
local  angular  rocks  and  small  pieces  of  Oneida  and  Medina.  As  this  is 
on  the  top  of  a  crest  it  is  not  a  wash.  The  boulders  are  traced  towards 
the  Schuylkill  and  are  mainly  subangular  and  rough,  spheroid,  ovoid, 
some  waterworn,  some  old  and  surface-cracked.  They  finally  disappear 
before  reaching  the  river,  and  therefore  do  not  come  from  thence.  At 
Hamburg  the  slate  outcrops  vertically  beneath  a  cap  of  river  gravel,  not 
at  all  like  the  drift  3}^  miles  to  the  east. 

Between  Maiden  Creek  and  Shoemakersville,  however,  the  drift- 
sheet  is  carried  continuously  to  Schuylkill  River.  Wells  at  this  place 
pass  through  12  feet  of  " Schuylkill  River  Bottom"  and  10  feet  of 
"gravel"  to  reach  the  slate  floor.  It  is  but  10  feet  thick,  and  most  of  the 
wells  stop  in  it  so  as  to  find  soft  water,  while  others  pass  through  it  and 
end  in  the  limestone.  The  tip  of  the  tongue  of  No.  3  crossed  the  river 
between  this  place  and  Hamburg.  Figure  11  shows  the  slate  decayed 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3 


31 


and  outcropping  vertically.     This  is  in  a  railroad  cutting  which  exposes 
no  hard  slate.     Three  hundred  feet  south  a  channel  has  been  broadly 


FIG.  11. — Cutting  in  Hudson  slate  decaying  in  place,  between  Shoemakersville  and 

Hamburg,  Berks  Co. 


FIG.  12. — Cutting  in  drift  of  slate  flakes  enclosing  polished  sandstone  boulders  and 
cobbles,  300  feet  south  of  last  figure,  Shoemakersville,  Berks  Co. 

scooped  into  this  soft  bed  and  filled  with  land-laid  drift,  as  shown  in 
Figure  12.     The  body  of  the  drift  is  of  slate  slabs  and  flakes  with  little 


32  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

or  no  sand,  including  glaciated  and  polished  sandstone  cobbles  and  small 
boulders.  At  times  this  carries  sporadic  bodies  of  rolled  gravel,  and  in 
places  it  is  capped  thereby.  This  is  an  unstratified  land-laid  drift  with 
materials  brought  from  the  eastward.  On  the  west  side  of  the  river, 
opposite  Shoemakersville  is  a  cutting  through  the  capping  of  a  slate 
quarry.  It  shows  large  and  small  slabs  lying  at  all  angles  north  of  Center- 
port,  Figure  13,  and  indicates  the  removal  of  a  considerable  cap  of  de- 
cayed surficial  mantle. 

Attention  is  called  to  the  need  of  study  of  the  valley  of  Tulpehocken 
Creek,  which  debouches  upon  the  Schuylkill  Valley  at  Reading.     The 


FIG.  13. — Drift  at  extreme  edge  of  ice-sheet,  Centerport,  Berks  Co. 

portion  of  interest  is  its  branch  called  Northkill  Creek,  which  rises  below 
Northkill  Gap,  5  miles  west  of  Schuylkill  Gap — both  in  Kittatinny 
Mountain.  Mr.  Barrell  reported  that  the  flood-plain  contains  rolled 
water-worn  and  semiangular  Medina  and  red  sandstone  (Hudson)  cobbles 
up  to  6  inches  in  diameter  which  could  not  be  traced  over  50  feet  above 
the  creek.  The  soil  is  the  usual  aggregate  of  slate  flakes  without  gravel. 
If  the  cobbles  were  distributed  by  water  there  should  be  sand  and  siltjn 
the  mixture,  and  perhaps  gravel. 

Glacial  Lake  Packer  and  the  Glacial  History.— The  area  can  be  found 
by  marking  the  500-foot  contour  of  the  Easton,  Slatington  and  Allentown 
quadrangles.  The  restraining  col  was  at  Topton,  about  495.  Leithsville 
col  was  covered  by  the  ice-sheet.  The  Delaware  narrows  below  Riegels- 
ville  was  closed  either  by  the  ice-sheet  or,  after  that  was  stagnant,  by 
icebergs  from  No.  2,  which  was  crossing  the  river  above  Stroudsburg. 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3  33 

The  lake  level  is  marked  by  the  stopping  of  Packer  Clay  (Early  Broad 
Mountain  A)  at  or  about  500  near  White  Hall,  Jacksonville  (Northamp- 
ton Co.),  Bath,  Laury's,  Bowman's  and  Parry ville.  North  of  Lehigh 
Gap  it  extends  slightly  above  500.  At  Parryville  it  is  overlaid  by  out- 
wash  from  No.  2,  and  is  thus  not  an  outwash  from  the  great  moraine, 
but  belongs  entirely  to  the  First  Phase,  as  does  the  entire  history  of  this 
lake,  which  had  three  periods : 

First  Period. — Preglacial  Flooding. 

Second  Period. — Glacial  Occupation. 

Third  Period. — Clearing  of  Stagnant  Ice  from  the  Lake  Area. 

First  Period.  Preglacial  Flooding. — No  deposits  other  than  orogenic 
slope-washes  have  been  found.  The  flow  in  the  Lehigh  and  affluents 
would  be  that  of  an  abnormal  spring  thaw.  This  period  might  be  a  long 
one,  as  clogging  of  Delaware  narrows  would  begin  as  soon  as  bergs  could 
reach  it.  The  glacial  ablation  came  with  No.  3,  and  the  latter  reached 
Port  Jervis  and  the  Delaware  trough,  55  miles  above  the  Mouth  of  Lehigh 
River,  where  bergs  could  be  calved  readily,  centuries  before  the  glacial 
front  arrived  at  Easton.  This  time  should  be  sufficient  to  leave  records 
of  ponding,  were  it  not  for  the  covering  of  the  lake  bed  by  ice,  and  the 
subsequent  scour  that  reached  to  its  rock  floor. 

Second  Period.  Glacial  Occupation. — To  cross  Kittatinny  and  South 
mountains  the  ice-sheet  at  Easton  must  have  been  1250  feet  thick 
and  1000  at  Allentown,  with  average  weight  of  35  tons  per  square 
foot  of  surface  along  the  Lehigh  trough  between  those  places.  The 
drift  of  this  period  has  been  named  Early  Great  Valley.  From  a  study  of 
the  profile  of  the  trough  of  Lehigh  River  between  Mauch  Chunk  and 
Easton  it  is  possible  that  it  has  been  trenched  40  feet  at  Allentown. 
The  fall  between  the  first  and  Lehigh  Gap  is  7.5  feet  per  mile; 
thence  to  Allentown,  10  feet;  thence  to  Glendon,  4.23  feet;  thence  to 
Easton  7.5.  An  average  grade  of  7.5  between  Mauch  Chunk  and  Easton 
would  elevate  the  bed  at  Allentown  40  feet.  That  is  the  depth  of  the 
drift  filling  at  South  Bethlehem  (Steel  Works),  and  as  the  trench  walls 
between  New  Nisky  Cemetery  and  the  limestone  outcrop  south  of  the 
Steel  Works  rise  over  20  feet  above  the  river  bed,  the  Lehigh  trench  there 
is  over  60  feet  deep,  and  with  steep  walls.  This  trenching  may  be  merely 
the  crushing  of  the  roofs  of  a  series  of  caverns  along  the  outcrop  of  the 
limestone  immediately  adjacent  to  the  Lehigh  trough  between  Allentown 
and  Easton,  and  along  the  flank  of  South  Mountain  west  of  Allentown. 
These  last  have  been  broken  in  and  filled  with  drift  varying  in  thickness 
from  20  feet  at  Alburtis  to  over  89  at  Topton,  with  greater  thicknesses 
farther  west.  From  these  caverns  much  of  the  limonite  has  been  taken, 
and  in  them  there  is  the  same  sequence  of  drift  sheets  that  obtains  on 
the  surface  of  the  limestone  valley  (preface  note  B,  p.  296).  In  connec- 
tion with  this  trenching  of  the  Lehigh  trough  is  the  discovery  of  the  pre- 


34  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

glacial  bed  of  the  Monocacy  against  the  granulite  rock  floor  at  Twelfth 
Avenue,  West  Bethlehem,  160  feet  below  the  crest  of  the  hill,  and  far 
below  the  present  water  level.  This  would  indicate  a  discharge  into 
Lehigh  River  at  the  great  bend  near  Geisingers,  and  would  also  be  in 
accord  with  Mr.  Barrell's  suggestion  that  Lehigh  River  long  before  the 
glacial  period  passed  through  Leipert's  Gap  in  South  Mountain  into  the 
Perkiomen-Schuylkill  basin.  This  flow  may  have  been  at  the  time  when 
there  was  a  river  flowing  through  the  Wind  Gap.  A  study  of  this  region, 
however,  may  connect  this  Gap  with  the  advent  of  No.  3. 

Third  Period.     Clearing   of  Stagnant   Ice  from  the  Lake   Area 

Late  Great  Valley  Drift.  Early  Ablation  Division.  Strong  Currents. 
— In  the  scheme,  the  strength  of  the  currents  was  laid  to  the  narrowness 
of  the  channel  torn  through  the  stagnant  ice.  This  seems  to  be  substan- 
tiated by  the  intensity  of  the  scouring  of  the  rock  floor  and  the  removal  of 
the  land-laid  drift  along  the  current  lines.  Had  the  strength  of  current 
depended  upon  a  possible  increase  of  snow-cap  incident  to  the  arrival  of 
No.  2  over  the  Lehigh  headwaters  there  should  have  been  a  continuation 
— even  an  increase — in  that  strength  as  the  lobe  itself  gained  and  covered 
the  same.  On  the  contrary,  the  strength  of  current  diminished  and  at 
the  end,  when  No.  2  actually  covered  those  headwaters,  the  slackest 
current  on  record  obtained,  as  will  be  seen  by  the  increasing  fineness  of 
the  grains  in  the  deposits.  This  decrease  in  current  velocity  can  be 
associated  with  increase  in  current  volume  if  the  cross-section  of  the 
channel  increases  more  rapidly  than  does  the  latter.  The  conclusion  is 
thus  forced  that  the  channel  torn  through  the  stagnant  ice  was  broadened 
by  the  erosive  force  of  the  current  aided  by  the  calving  of  the  margin  into 
the  open  area  as  the  ice-sheet,  during  ablation,  settled  towards  the 
regional  trough. 

This  current  through  the  gradually  increasing  area  of  clearance  would 
have  dropped  its  bulky  burden  at  Mauch  Chunk  as  soon  as  the  level 
of  ponding  was  reached.  The  deposits  of  the  time  are  therefore  disasso- 
ciated with  No.  2  and  influences  north  of  that  Gap,  and  confined  to  the 
decaying  ice-sheet.  This  is  the  reason  for  calling  the  following  "  Abla- 
tion" divisions. 

The  Deposition  of  Rock  Masses  and  Boulders. — The  line  of  current 
seems  to  have  passed  north  of  the  granulite  hill  opposite  Allentown  on 
the  east  bank  of  Lehigh  River.  Later  there  seems  to  have  been  a  clear- 
ance over  the  present  river  channel,  and  a  current  south  of  this  hill 
also,  with  a  long  line  of  slacker  water  just  east  of  the  hill,  as  obtains  below 
each  pier  of  a  bridge.  This  current  took  a  short  cut  from  Catasauqua 
to  Bethlehem  north  of  Rittersville.  It  would  strike  South  Mountain 
over  South  Bethlehem,  and  probably  cleared  away  the  stagnant  ice 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3  35 

there  over  an  area  extending  westward  to  include  the  end  of  Fountain 
Hill  immediately  west  of  the  Episcopal  Church,  where  there  seems  to 
have  been  an  eddy. 

The  discovery  of  the  accumulation  of  boulders  that  " splashed" 
into  the  preglacially  decayed  rock  floor  at  East  Allentown  has  been  told 
in  chapter  four.  They  were  dropped  at  this  time.  While  their  sizes 
tell  only  of  ice-cakes  of  moderate  size,  there  are  large  masses  found  near 
the  bottoms  of  the  kames  along  the  Lehigh  banks  that  tell  of  larger  bergs, 
and  especially  on  the  edge  of  Fountain  Hill  is  a  pile  of  large  masses  at 
least  10  feet  thick,  one  of  which  measured  11X4X3  feet.  These  seem 
to  have  been  dropped  by  the  grinding  of  bergs,  or  their  collision,  rather 
than  by  ablation.  We  can  picture  the  surface  of  the  stream  covered  by 
bergs  and  cakes  which  were  hurried  to  the  clogging  in  the  Delaware 
narrows.  There  was  not  a  sign  of  clogging  in  the  Lehigh  channel.  The 
water  was  at  least  250  feet  deep  over  the  decayed  floor  at  East  Allen- 
town.  The  boulders  that  "splashed"  into  its  soft  surface  did  so  at  an 
angle  of  40°  with  the  vertical,  and  thus  showed  a  swift  motion  in  the 
ice-cakes  from  which  they  were  dropped.  This  period  was  followed 
immediately  and  without  unconformity  by  the 

Late  Ablation  Division.  Slackening  to  Slow  Currents. — The  channel 
south  of  the  East  Allentown  granulite  hill  seems  to  have  been  cleared 
away  at  this  time  and  a  strong  current  passed  there,  while  there  was 
an  area  of  slackened  water  4  miles  long  behind  that  hill,  extending  from 
it  to  the  present  Monocacy  channel  between  Bethlehem  and  West 
Bethlehem.  The  current  south  of  the  granulite  hill  dropped  cobbly 
drift  between  Allentown  and  South  Bethlehem,  resembling  that  of  Figure 
3,  dropped  under  exactly  similar  conditions  where  Glacial  Lake  Lesley 
was  discharging  its  waters  similarly  filled  with  ice-cakes  over  the  col  at 
Dix,  Blair  County,  but  differing  in  being  better  rolled.  They  can  be 
seen  in  the  many  cuttings  along  Lehigh  Valley  Railroad.  The  currents 
were  over  12  inches  per  second  and  less  than  4  feet.  Behind  the  granulite 
hill  they  varied  between  6  and  11  inches  per  second,  and  dropped  in 
wavy  layers  interstratified  sands  and  fine  gravels — both  free  from  silt 
and  clay — in  which  were  dropped  very  infrequent  small  cobbles  and  at 
long  intervals  apart  a  small  boulder.  Figure  14  shows  the  working 
face  at  Rauch's  Pit  in  1897.  The  Monocacy  gorge  is  J^  mile  to  the 
right,  and  the  influence  of  its  current  is  seen  in  the  foreset  dip  of  the 
gravels  to  that  side  and  the  subsequent  smoothing  along  a  plane  dipping 
to  the  right.  The  pile  of  small  cobbles  in  the  foreground  is  of  rolled 
pieces  dropped  by  ice-cakes.  An  examination  of  the  working  face  shows 
no  boulders.  The  writer  has  notes  of  less  than  6  during  25  years  of 
examination.  Mr.  Lesley  used  this  absence  of  boulders  to  attribute  this 
bar  to  an  old  "high-level"  river  bed  (Letter  of  transmission,  vol.  D3. 
2d.  Geol.  Surv.  Pa.,  1878).  At  Twelfth  Avenue,  West  Bethlehem, 


36  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

slightly  below  the  crest  of  the  formation,  a  well  was  driven  160  feet 
through  it  to  reach  the  granulite  rock  floor  below  the  present  Lehigh 
water  level. 

Another  point  of  interest  of  this  division  is  the  almost  equally  huge 
bar  extending  eastwardly  from  the  end  of  South  Mountain,  on  which 
Northampton  Heights  is  built.  Figure  2  is  taken  from  the  track  at  the 
bottom  of  a  deep  cutting  where  the  Philadelphia  &  Reading  Railroad 
passes  about  the  end  of  the  mountain.  The  depth  of  the  cut  can  be 
measured  by  noting  the  height  of  the  telegraph  poles.  This  track  level 
is  100  feet  above  the  Lehigh  River.  The  Lehigh  channel  immediately 
opposite  this  is  rilled  with  drift  for  40  feet.  The  top  of  the  bar  is  thus  at 


FIG.  14. — West  Bethlehem  gravels  overlaid  unconformably  by  Packer  Clay,  Ranch's 
Pit,  West  Bethlehem,  Lehigh  Co. 

least  200  feet  above  the  rock  floor  of  the  Lehigb.  The  gradual  shading 
of  thickness  of  strata  and  of  sizes  of  pieces  from  the  center  line  of  this 
bar  to  the  Saucon  Valley  to  the  south,  and  the  Lehigh  Valley  to  the 
north,  indicate  an  equally  strong  current  from  each  moving  towards 
Easton.  This,  in  turn,  proves  that  the  Leithsville  col  at  450  was  covered 
by  the  stagnant  ice,  and  that  there  was  no  movement  of  current  from 
the  Lehigh  into  Saucon  Valley.  This  condition  continued  through  the 
ablation  of  the  stagnant  ice,  and  will  be  referred  to  below. 

It  remains  to  speak  of  the  character  of  the  gravels  and  sands  dropped 
during  this  division.  There  is  an  inch  of  limonite  hardpan  (see  preface 
note  B,  p.  291  and  Figure  11)  beneath  the  gravels  at  Rauch's  Gravel 
Pit,  showing  that  the  gravels  here  were  either  preglacially  stained  or 
were  affected  by  the  seepage  from  the  highly  ferruginous  Packer  Clay 


GREAT  VALLEY  DRIFT.    LOBE  NO.  3  37 

above.  There  is  no  impervious  stratum  above  them  here,  and  the 
latter  suggestion  is  the  correct  one,  as,  at  Twelfth  Avenue,  the  same 
gravels  are  capped  by  4  to  5  feet  of  quicksand  and  rock  meal  of  light 
color  and  impervious  character,  on  which  are  from  28  to  30  feet  of  the 
above  clay.  The  writer  sank  a  shaft  for  a  sewage  opening  over  70  feet 
into  the  bar,  through  28  feet  of  clay,  5  of  quicksand,  and  40  feet  into  the 
stratified  gravels,  which  were  as  clean  and  fresh  as  those  in  the  Lehigh 
river  bed.  The  gravels  were  thus  clean  when  laid  down.  These  gravels 
and  the  overlying  quicksands  at  Twelfth  Avenue,  above  are  the  Late 
Ablation  Division,  A  and  B,  of  the  Scheme,  and  the  smoothing  of  the 
top  of  the  gravels  in  Rauch's  Pit  referred  to  immediately  above  is  the 
part  C  of  the  same. 

Broad  Mountain  Drift.  Lobe  No.  2. — We  now  come  to  the  evidences 
of  the  arrival  of  No.  2  over  the  headwaters  of  Lehigh  River  after  the 
clearing  of  the  basin  of  Lake  Packer  from  ice  and  the  passage  of  clear 
water  to  smooth  the  surface  of  the  upper  of  the  deposits  from  the  abla- 
tion of  the  ice-sheet.  This  is  in  accord  with  the  calculation  made  in 
chapter  two,  where,  with  a  maximum  advance  of  100  feet  per  annum, 
No.  3  would  reach  its  farthest  bounds  over  9000  years  before  No.  2 
would  pass  the  Lehigh  watershed,  or  eliminating  the  rate,  it  would  take 
No.  3  six-elevenths  of  the  period  to  reach  its  farthest  extension  that 
No.  2  would  require  to  cross  the  above  watershed.  This  would  allow 
for  a  sufficient  extension  of  the  activity  of  No.  3  to  bring  to  the  Saucon 
Valley  the  three  rock  trains,  the  most  northern  and  latest  of  which 
would  reach  its  present  position  about  1000  years  after  the  arrival  of 
the  front  of  the  lobe  at  Schuylkill  River.  This  period  of  activity  would 
be  sufficient  to  hollow  the  Punch  Bowl  out  of  the  southern  flank  of 
Kittatinny  Mountain  near  Bake  Oven  Knob. 

Early  Broad  Mountain  Period.  Outwash.  Packer  Clay. — This 
brownish-red  sandy  silt  covers  everything  in  the  Lehigh  basin  below 
500  feet  above  ocean  level,  and  is  absent  from  Saucon  Valley — being 
there  replaced  by  a  thick  slope-wash  near  the  bordering  hills,  and  a 
thinner  wash  over  the  valley  floor.  The  Saucon  wash  varies  from  that 
in  the  Lehigh  Valley  both  in  its  lack  of  thickness  and  in  the  absence  of 
the  iceberg  inclusions  which  abound  over  the  Lehigh  basin.  The  increase 
in  volume  which  obtained  north  of  Lehigh  Gap  was  insufficient  to  pro- 
duce over  the  general  line  of  flow  through  the  ponded  area  of  Lake  Packer 
a  current  greater  than  3  inches  per  second.  This  in  itself  indicates  a 
large  cleared  area  and  a  movement  of  water  towards  the  Delaware  ex- 
tending from  Nazareth  to  Emaus,  or  entirely  across  the  flooded  area. 
The  thickness  of  the  clay  varies  from  6  to  30  feet.  It  is  over  10  feet 
thick  at  Nazareth,  17  at  Emaus,  30  to  10  over* the  West  Bethlehem  bar, 
6  at  Northampton  Heights  and  Bethlehem.  Figure  14  shows  its  thick- 


38 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


ness  and  appearance  at  Ranch's  Pit,  West  Bethlehem,  with  the  cobbles 
and  small  boulders  scattered  through  it.  Figure  15  is  the  face  of  the 
brick  working  north  of  Bethlehem  and  \Y±  miles  northeast  of  the  gravel 


FIG.  15.— Packer  Clay,  Brick-yard,  Bethlehem,  Nhn.  Co. 


FIG.  16. — Packer  Clay,  Brick-yard,  East  Allentown,  Lehigh  Co. 

pit.  Here  the  clay  is  cleaner,  but  it  contains  pieces  brought  by  ice- 
cakes,  among  which  the  writer  found  some  fragments  of  the  decayed 
anthracite  outcrop  which  resembled  the  half-consumed  pieces  of  the  same 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3 


39 


after  quenching  and  washing  free  from  ash.  This  decay  is  not  post- 
glacial, as  the  cracks  and  corrosions  of  the  surface  of  the  pieces  were 
filled  with  clay,  which  was  readily  washed  therefrom  by  a  weak  jet  of 
water.  The  subject  of  decay  in  anthracite  will  be  fully  considered  in 
the  analyses  of  Morea  coals.  Micaceous  sandstone  from  the  coal  is 
also  found  in  this  clay  to  prove  that  it  is  the  levitated  surficial  mantle 
of  the  Lehigh  Headwaters.  No  vegetable  mixture  is  discernable,  and 
there  is,  as  far  as  known,  no  bluing  of  the  clay  through  reduction  of 
ferric  salts.  Figure  16  shows  the  fag-end  of  the  clay  cap  at  the  abandoned 
brick  working  at  East  Allentown.  Here  it  was  15  feet  thick.  Figure 
17  is  a  section  at  Stemton,  near  Lehigh  River,  showing  the  rounded 
character  of  the  boulders.  The  smoothed  rock  projection  in  the  middle 


FIG.  17. — Packer  Clay,  on  kame,  60  feet  above  Lehigh  River,  Stemton,  Nhn.  Co., 
including  polished  Pocono  cobbles  (iceberg  burden). 

foreground  is  the  fresh  and  glaciated  limestone  outcrop.  Its  covering 
by  a  gravel  outwash  at  Parryville  shows  that  it  belongs  to  the  First 
Phase,  and  is  not  art  outwash  from  the  great  moraine.  This  is  also 
substantiated  by  the  cleanness  of  the  clay  in  the  filled  sink-hole  at 
Nazareth  on  the  northern  border  of  the  limestone  outcrop,  and  but  6 
miles  southwest  of  the  great  moraine. 

Kittatinny  Mountain. — This  is  locally  called  the  Blue  Ridge.  It 
averages  1550  above  ocean  level,  with  a  crest  of  Oneida  conglomerate, 
with  Medina  sandstone  immediately  to  the  north  of  the  crest,  and  with 
Clinton  forming  the  lower  half  of  the  northern  flank.  The  ice-sheet 
readily  crossed  this  ridge  in  New  Jersey  as  it  was  nearer  the  northern 


40 


PENNSYLVANIA  GLACfATION.    FIRST  PHASE 


part  of  the  trough  in  which  No.  3  moved.  West  of  Delaware  River 
it  was  a  dividing  line  one-fourth  of  the  way  from  the  Pocono  to  the 
Granulite  ridges  between  which  the  lobe  moved,  and  thus,  with  abundant 
room  to  the  north,  there  was  a  change  from  the  push  over  the  ridge  to  a 
movement  almost  parallel  with  its  crest,  and  thus  with  the  strikes  of  the 
outcrops  of  the  rocks  that  formed  it.  The  huge  masses  of  Oneida 
conglomerate  south  of  it  on  the  slate  belt  did  not  move  directly  south, 
but  came  from  its  crest  far  to  the  east.  These  are  very  abundant  west 
of  Slatington,  and  thin  out  till  south  of  Bake  Oven  Knob  one  solitary 
mass  is  found.  That  there  was  a  crossing  of  the  ridge  is  proved  by 
finding  Oriskany  cobbles  and  pebbles  close  against  the  southern  flanks 


FIG.  18. — Accumulation  of  Oneida  conglomerate  masses  where  working  face    of 
glacier  crossed  Kittatinny  Mountain  at  Bake  Oven  Knob. 

as  far  west  as  Wanamakers.  This  crossing  was,  however,  at  such  a 
slight  angle  that  the  pieces  picked  up  from  an  outcrop  were  left  on  the 
same  farther  west.  Figure  18  shows  such  a  heaping  of  the  Oneida  con- 
glomerate at  the  crest  of  Bake  Oven  Knob,  from  which  the  gravels  and 
sands  have  been  completely  removed.  Figure  19  shows  the  crest  west 
of  the  Knob,  where  there  is  cultivated  soil.  A  well  near  the  Mountain 
House  on  the  road  to  Kepner  is  sunk  30  feet  in  gravel.  On  the  southern 
flank  the  drift-sheet  is  almost  purely  local  and  angular.  On  the  northern 
flank  Oriskany  cobbles  are  carried  towards  the  crest  on  the  Kepner  road, 
and  are  found  along  that  flank  almost  to  Rene  Mont.  The  ice  was  thus 
astride  the  crest  within  3J^  miles  of  Schuylkill  River.  The  finding  of 
the  drift-sheet  east  of  Hamburg  shows  the  possibility  of  the  extension 


GREAT  VALLEY  DRIFT.  LOBE  NO.  3  41 

of  an  ice-tongue  into  the  wedge-end  behind  the  Offset,  if  not  into  its  lower 
loop,  below  whose  opening  the  above  drift  was  found. 

The  carriage  of  the  500-foot  contour  deeply  into  the  southern  flank 
of  the  ridge  south  of  Bake  Oven  Knob  has  been  noted  above.  It  seems 
probable  that  a  surficial  stream  from  the  glacier  fell  1000  feet  against 
this  flank  and  hollowed  the  Punch  Bowl  as  we  find  it  today.  That  some- 
thing extraordinary  occurred  within  a  small  area  is  shown  by  the  Punch 
Bowl,  the  deep  trenching  of  the  many  affluents  of  Ontelaunee  Creek  and 
the  200  foot  drop  of  2  miles  of  the  ridge  crest.  This  region  deserves 
careful  study.  It  is  possible  now  to  draw  the  boundary  of  the  Attenuated 
Border  from  the  mountain  flank  south  of  Mountainville,  on  the  saddle 
between  Saucon  and  Great  Valley,  along  South  Mountain  northern  flank 


FIG.  19. — Smooth  and  cultivated  crest  of  Kittatinny  Mountain  west  of  Bake  Oven 

Knob. 

to  Temple,  where  it  passes  across  the  valley  in  a  loop  enclosing  Center- 
port,  on  the  west  side  of  Schuylkill  River,  and  returning  to  pass  around 
the  Offset  fault  of  Kittatinny  Mountain  and  reach  the  crest  of  the  latter 
3J^  miles  east  of,  Schuylkill  River. 

The  Lower  Helderburg  and  Marcellus  Valleys. — These  are  bounded 
on  the  south  by  Kittatinny  Mountain  and  on  the  north  by  Mauch  Chunk 
(Pocono)  Mountain.  There  is  a  slight  Oriskany  ridge  and  a  more  preten- 
tious Catskill  one  west  of  Lehigh  River,  which  is  all  of  the  region  that 
will  be  considered,  as  the  tracing  of  the  boundary  is  all  that  will  be  at- 
tempted. The  presence  of  native  copper  is  reported  in  the  eastern  end 
of  this  region,  in  Monroe  County,  by  Dr.  Albert  G.  Rau  of  the  Moravian 
College. 


42 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


The  Lower  Helderberg  (Lizard  Creek)  Valley  is  the  deeper  and  con- 
tains throughout  an  abundance  of  rolled  and  sand-poor  gravel  of  fresh 


FIG.  20. — Railroad  cutting  through  moraine  west  of  Kepner  saddle,  Schuylkill  Co. 


FIG.  21. — Cobbles  from  gravelly  drift,  Balliet,  Carbon  Co. 

appearance,  which  is  cut  through  many  times  by  the  railroad.  This 
disappears  on  the  col  at  Kepner,  and  is  therefore  due  to  the  ponding  of 
Lake  Packer.  The  moraine  at  Kepner  is  1  mile  west  of  that  station, 


BROAD  MOUNTAIN  DRIFT.    LOBE  NO.  2  43 

and  the  railroad  cutting  is  deep,  as  shown  in  Figure  20.  There  is  a  steep 
slope  westward  to  the  Little  Schuylkill  trough  with  a  wash  upon  it,  which 
may  overlie  drift  as  elsewhere  near  the  boundary  of  this  and  the  great 
moraine.  The  railroad  cuttings  beyond  Kepner  show  no  gravel  or  any 
cap,  but  their  tops  seem  to  carry  a  thinner  and  a  fresher  capping  than 
would  obtain  in  an  unglaciated  region,  and  it  is  probable  that  the  clear 
ice-front  went  farther  west  and  south.  Figure  21  shows  the  Lizard 
Creek  drift  at  Balliet. 

The  movement  of  the  ice-sheet  parallel  to  the  strikes  of  the  forma- 
tions makes  the  drift-sheet  monotonous  over  the  higher  and  more  broken 
Marcellus-to-Catskill  region  south  of  the  lofty  barrier  of  Mauch  Chunk 
Mountain.  Pottsville  conglomerate  is  found  on  a  crest  between  Penns- 
ville  and  Lehighton,  which  may  have  come  via  Lehigh  River.  More 
definite  and  convincing  evidences  of  the  passage  of  the  southern  margin 
of  Lobe  No.  2  over  Mauch  Chunk  Mountain  and  upon  the  Catskill 
border  will  be  described  in  the  next  chapter  where  this  lobe  is  studied.  It 
remains  to  say  that  in  the  land-laid  drift  of  No.  3  no  rocks  have,  thus  far, 
been  found  above  Pocono. 


CHAPTER  VI 
BROAD  MOUNTAIN  DRIFT.     LOBE  NO.  2 

The  Champlain-Mohawk-Delaware-Shamokin  lobe  moved  over  the 
Delaware  watershed,  the  eastern  boundary  of  Pennsylvania,  the  Moosic- 
Pocono  ridge,  the  Lehigh  headwaters,  the  Middle  and  part  of  the  South- 
ern Anthracite  basins,  and  stopped  against  Susquehanna  River.  From 
the  outcrops  crossed,  the  rocks  to  be  expected  in  the  drift-sheet  extend 
from  Cambrian  to  Pennsylvanian,  but  the  crossing  of  the  Mohawk  and 
Delaware  troughs  twice  eliminated  the  basal  burden,  so  that  within  the 
Attenuated  Border  we  find  only  the  local  Mississippian-Pennsylvanian 
fragments  as  the  bulk  of  the  drift,  with  extremely  rare  foreigners,  such 
as  limestone,  and  less  rare  shales  near  the  Catskill.  The  rocks  most 
common  begin  with  the  Pocono,  which  was  at  the  top  of  the  column  in 
the  drift  of  No.  3,  and  so  the  sheets  of  these  two  lobes  differ  almost  com- 
pletely. Of  the  local  outcrops  covered  there  are  360  square  miles  of 
Mauch  Chunk  red  shale  west  of  Lehigh  River,  and  a  total  length  of  84 
miles  of  the  same  in  the  narrow  valleys  bordering  the  basins  between  the 
Lehigh  and  Susquehanna  rivers,  and  yet  there  is  not  a  large  proportion 
of  Mauch  Chunk  in  the  drift.  The  highest  elevations  are  over  the  Potts- 
ville conglomerate  anticlinal  north  of  Morea  (2100),  and  the  broad  moun- 
tains are  of  the  same  formation.  In  fact,  No.  2  crossed  14  Pottsville 
outcrops  between  Bear  Creek  and  the  spoon-end  of  Little  Mountain 


44  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

(Pocono),  against  which  the  tip  of  the  lobe  massed  itself.  The  drift- 
sheet  is  thus  mainly  Pottsville  with  some  red  shale  and  the  micaceous 
and  other  sandstones  of  the  coal,  and  only  the  presence  of  these  in  incon- 
siderable amounts  enables  us  at  times  to  distinguish  it  from  the  decayed 
mantle  over  an  unglaciated  Pottsville  outcrop.  The  area  covered  by 
No.  2  is  thus  divided: 

The  Southern  Basin. 
The  Pottsville  Anticlinal. 
The  Western-Middle  Basin. 

Before  describing  the  glacial  phenomena  in  these  basins  it  is  necessary 
to  say  that  the  wet  preparation  of  coal  has  filled  the  streams  and,  when 
ponded,  the  valleys,  many  feet  deep  with  culm,  so  that  the  old  stream 
bottoms  and  valley  floors  are  not  only  masked  but  obliterated.  The 
old  methods  of  working  have  permitted  the  anthracite  outcrops  to  cave  in. 
The  monotonous  Pottsville  composition  of  the  drift  requires  an  absolutely 
fresh  section  for  study,  and  such  can  be  found  only  at  the  headwaters  of 
the  small  affluents  of  the  main  streams.  The  tendency  to  slabbiness  in 
the  sandstones  of  the  coal  has  rolled  not  only  the  rounded  masses  and 
gravel  derived  therefrom,  but  even  the  pebbles  of  the  Pottsville  conglom- 
erate from  the  stream  bottoms,  unless  ponding  of  water  prevailed.  In 
consequence,  although  the  upper  part  of  the  West  Philadelphia  gravels 
passed  through  the  streams  of  the  Southern  Basin  which  were  covered 
by  the  ice-sheet,  the  regional  stream-bottoms  are  almost  everywhere 
slabby.  Now  and  then  they  have  been  cut  into  a  flood-plain  containing 
boulders  and  gravel.  The  accurate  marking  of  the  boundary  of  the 
Attenuated  Border  is  therefore  more  difficult  over  this  region.  Another 
difficulty  results  from  the  sheer  rise  of  the  two  borders  (Pocono  and 
Pottsville)  above  the  basins  and  their  intervening  Mauch  Chunk  Valley. 
These  caught  No.  2  within  their  grip  and  forced  it  to  move  along  the 
strikes  of  the  measures,  so  that  the  drift  is  locally  monotonous,  and  its 
identification  depends  on  the  foreigners,  or,  where  a  ridge  has  been 
crossed,  on  the  crestal  blocks  carried  onward  into  the  valley  beyond. 

The  Southern  Basin.  Panther  Creek. — This  is  the  extreme  eastern 
end  of  the  basin  and  rests  against  Lehigh  River,  so  that  there  is  no  doubt 
of  its  glaciation.  The  point  at  issue,  however,  is  whether  the  edge  of  No. 
2  crossed  Mauch  Chunk  Mountain  (Pocono).  Masses  of  the  Pottsville 
inner  rim  of  the  basin  can  be  traced  from  Summit  Hill  across  the  red 
shale  valley  to  within  100  feet  of  the  outer  Pocono  rim,  and  masses  of  the 
latter  and  pieces  of  Pottsville  are  found  in  the  3-foot  drift-sheet  on  the 
road  to  Bloomingdale  at  1049  above  ocean  level.  This  sheet  also  carries 
micaceous  sandstone  of  the  coal  and  slabs  and  flakes  of  red  shale,  and  can 
be  found  just  east  of  Little  Schuylkill  Gap  in  Mauch  Chunk  Mountain. 
The  drift  of  No.  2  thus  intrudes  upon  that  of  No.  3,  and  settles  the  point 
queried  in  the  end  of  the  last  chapter.  The  boundary  of  the  Attenuated 


BROAD  MOUNTAIN  DRIFT.    LOBE  NO.  2  45 


Border  can  be  drawn  from  the  point  on  Kittatinny  crest,  3J^  miles  east 
of  Schuylkill  River  in  a  slanting  direction  so  as  to  pass  about  the  moraine 
west  of  Kepner,  and  almost  to  Rene  Mont,  and  thence  to  the  Little 
Schuylkill  Gap  just  above  mentioned. 

Tamaqua.  —  The  above  Gap  is  less  than  1  mile  south'  of  Tamaqua. 
The  Mauch  Chunk  red  shale  on  the  east  side  of  it  is  crushed  southward 
by  the  ice.  The  ice-sheet  ponded  the  water  for  4  miles  southwest  of 
Tamaqua,  so  that  for  this  distance  to  the  divide  beyond  where  are  the 
headwaters  of  Schuylkill  River,  there  is  abundant  rolled  gravel,  showing 
that  the  ice-sheet  crossed  the  divide  at  Tuscarora.  About  Tamaqua  are 
abundant  evidences  of  glaciation,  the  best  being  the  glaciated  coal  out- 
crop, opposite  the  railroad  station,  with  gravel  for  a  cap. 

Pottsville  Basin.  —  The  Southern  Basin  is  1  mile  broad  at  Tamaqua, 
2  at  Tuscarora,  and  3  at  Pottsville.  The  change  from  gravelly  drift  is 
not  sudden  on  the  divide.  It  is  found  both  in  the  stream  bottom  and  in 
the  flood-plain  at  New  Philadelphia,  6  miles  beyond  and  but  4  from 
Pottsville.  From  Cumbola  to  the  last  the  stream-bottom  is  slabby. 
Even  below  the  debouchment  of  Silver  .Creek  which  flows  over  a  drift 
bottom  cut  into  a  drift  flood-plain  it  remains  slabby,  so  that  no  value  can 
be  attached  to  the  slabbiness.  Silver  Creek  is  trenched  deeply  into  the 
Pottsville  conglomerate  anticlinal,  rising  near  the  highest  point  south 
of  Bear's  Head  (1680),  and  3  miles  southeast  of  Morea.  Its  bottom  is 
full  of  rounded  boulders.  The  ice-sheet  covered  the  area  where  Locust 
and  Broad  mountains  meet.  Leaving  the  question  of  how  much  nearer 
to  Pottsville  the  ice-sheet  came  till  later  we  now  consider  the  broad 
area  of  the  Pottsville  anticlinal. 

The  Pottsville  Anticlinal.  Morea.  —  Reference  is  first  made  to  preface 
note  F,  where  the  glaciation  of  the  Morea  region  is  described.  Its  many 
illustrations  show  the  level  planing  of  the  vertical  northern  outcrop  and 
the  character  of  the  drift.  The  movement  southward  of  the  ice-sheet 
must  be  borne  in  mind  in  connection  with  the  fact  that  the  margin  of  an 
ice-sheet  is  supposed  to  have  little  or  no  erosive  power,  and  the  amount 
of  erosion  which  took  place  here  tells  that  a  great  weight  bore  down  on 
this  region,  and  that  the  margin  must  have  extended  farther  south,  espe- 
cially as  the  weighted  portion  which  performed  the  erosion  moved  south- 
ward. Figure  22  shows  the  south  outcrop  of  the  Mammoth  Bed  planed 
level  and  covered  by  8  feet  of  Pottsville  conglomerate  drift  in  which  are 
boulders  5  feet  in  diameter.  The  character  of  the  glaciated  coal  will  be 
noted  immediately  below.  The  weight  of  the  ice-sheet  is  shown  by  the 
high  polish  of  large  areas  of  conglomerate  near  Delano,  8J^  miles  north  of 
Morea.  Two  miles  south  of  the  latter  on  the  hillside  south  of  the  Eisen- 
huth  Reservoir  the  same  drift  overlies  the  outcrop  of  the  Lykens  (A)  Bed. 
In  it  was  found  a  pebble  of  non-fossiliferous  dove-colored  limestone 
(?Beekmantown,  Lowville,  Pamelia?).  The  same  drift  is  found  7  miles 


46  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

southwest  of  Morea  where  Mill  Creek  cuts  through  5  feet  of  drift  to  join 
Schuylkill  River,  865  feet  below  the  elevation  of  Morea.  Here  the  rock 
floor  is  red  shale,  but  the  drift  is  like  that  at  Morea.  The  lotoest  foot  of 
drift  varies  greatly,  as  will  be  seen  by  the  three  sections  taken  immediately 
over  the  Mammoth  (E)  Bed  at  Morea.  The  first  two  over  the  north 
outcrop;  the  third  at  the  extreme  western  end  of  the  spoon.  The  fresh 
and  light-colored  appearance  of  the  drift  is  well  shown  in  Figure  22. 

Section  1  was  taken  three  breasts  east  of  the  crossing  of  the  Pennsyl- 
vania Railroad;  2,  200  feet  east  of  (1). 


FIG.  22. — Glaciated  southern  outcrop  of  mammoth  bed,  Morea,  Schuykill  Co. 

Surface,  rising  slightly  from  north  to  south,  but  generally  level  over  the  basin. 
General  appearance  as  shown  in  Figure  22,  which  is  looking  east  along  the  south 
outcrop  with  slight  rise  in  surface  to  south. 

Sandy,  pebbly,  decayed  Pottsville  conglomerate  drift,  light-colored,  free  from 
clay,  including  boulders  and  masses  of  conglomerate  to  5  feet  in  diameter.  Thickness 
at  section  (1),  10  feet;  (2),  8  feet;  (3),  4^  to  5  feet. 


Below  this  are  the  following  different  deposits,  each  unstratified:     , 

(1).  Crushed  Anthracite  in  coarse  fragments,  solid  and  of  bright  luster,  1  foot. 

Yellowish-white  clay  including  only  small  white  quartz  pebbles  from  the  Pottsville 
conglomerate.  Clay  plastic,  one-half  inch  thick. 

Solid,  highly  polished  and  grooved  anthracite,  with  luster  as  bright  as  on  a  fresh 
fracture  of  the  same  bed  200  feet  down  the  dip. 

(2).  Crushed  Anthracite  fragments  identical  with  those  in  section  (1),  18  inches 
thick. 

Mealed  Anthracite,  dull  luster,  loose  and  dry,  three-fourths  of  an  inch. 


BROAD  MOUNTAIN  DRIFT.    LOBE  NO.  2  47 

Yellowish-white,  clean,  plastic  sandy  clay  with  no  inclusions,  1  inch. 
Crushed  Anthracite  fragments,  finer  than  above,  bright  luster,  one-fourth  to 
three-fourths  of  an  inch. 

Mealed  Anthracite,  dull  and  pasty,  three-fifths  of  an  inch. 

Solid,  polished,  grooved,  outcrop  of  bed,  as  above. 

(3).  Red  clay,  clean  and  without  inclusions,  1  foot. 

Reddish,  orogenic  drift,  4  inches. 

Rusty  drift  mixed  with  abundant  Anthracite  flakes,  2  feet. 

Partially  decayed  and  softened  outcrop  of  bed,  duller  than  above  outcrops. 

The  lowest  layer  of  the  last  section  is  traced  for  some  distance  to  the 
south  to  show  the  direction  of  the  movement  of  the  ice,  and  is  very  well 
shown  in  Figure  2  (preface  note,  F),  extending  with  diminishing  color 
43  feet  across  the  picture  immediately  above  the  horizontally  planed 
bottom  sandstone.  This  tendency  of  No.  2  to  press  southward  here 
will  be  referred  to  when  the  end  of  the  lobe  is  reached  against  Susque- 
hanna  River.  The  boundary  of  the  Attenuated  Border  can  be  drawn 
through  the  Pocono  opening  at  Beaver  Creek  Gap  and  thence  in  the 
red  shale  (Mauch  Chunk)  valley  of  that  stream,  so  as  to  completely 
enclose  the  offset  fault  in  Second  Mountain  (as  Mauch  Chunk  Mountain 
is  known  west  of  Little  Schuylkill  Gap),  and  also  this 'gap.  Thence 
diagonally  along  Beaver  Valley  and  across  Sharp  Mountain  (as  Mount 
Pisgah  is  known  west  of  Little  Schuylkill  Gap)  to  Cumbola  and  St. 
Clair,  passing  2  miles  north  of  Pottsville.  A  more  careful  study  of  the 
Pottsville  vicinity  may  show  that  a  tongue  reached  that  city. 

The  Strippings.  Rates  of  Anthracite  Decay.— Stripping  is  a  method 
of  removing  the  overlying  rock  cover  of  a  bed,  so  that  the  latter  can  be 
entirely  removed  by  the  most  economical  and  safe  methods.  It  can  be 
employed  only  when  the  surface  is  valueless  and  the  cost  of  stripping  and 
mining  per  ton  of  the  bed  is  less  than  in  ordinary  underground  methods. 
By  stripping  the  cost  of  timbering,  lighting,  ventilation  and  complicated 
haulage  is  eliminated,  and  that  of  breaking-down,  loading  and  haulage 
reduced  two-thirds.  Morea  was  first  worked  by  the  underground  method 
and  then  stripped.  The  illustration  referred  to  in  the  preface  note,  F, 
above  shows  the  removal  of  the  cover  at  the  western  spoon-end  of  the 
basin. 

The  first  impression  of  a  mining  engineer  who  has  practiced  only  in 
unglaciated  regions  is  the  absence  of  " black  dirt"  and  of  decayed  and 
peacock  coal  at  the  outcrop  of  Morea;  the  next  is  the  absolute  sound- 
ness of  the  outcrop  of  the  bed,  and  the  brightness  of  its  luster  immediately 
beneath  the  clayless  and  porous  drift-sheet.  This  appears  wonderful 
when  it  is  understood  that  the  ice-sheet  which  polished  this  outcrop  came 
into  Pennsylvania  next  after  that  lobe  which  left  in  New  Jersey  and 
Pennsylvania  the  oldest  drift  in  the  region,  which  is  called  "  Jersey  an" 
and  "pre-Kansan."  In  other  words,  Anthracite  does  not  decay  as  fast 
as  its  enclosing  rocks.  The  5  to  15  feet  of  black  earth  which  outcrops 


48  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

in  unglaciated  areas  and  is  called  " black  dirt"  represents  the  decay  of 
the  bed  since  the  formation  of  the  Harrisburg  peneplain;  or  better,  the 
remnants  of  the  decay  after  the  sculpturing  incident  to  the  atmospheric 
erosion  of  the  regional  valleys  into  the  softer  formations. 

This  removal  of  the  black  dirt,  the  underlying  softened  lumps  sur- 
rounded with  still  softer  portions,  and  the  portions  of  the  bed  which  still 
showed  joint-planes  and  the  iridescent  blues  and  greens  thereon  which  is 
called  "  peacock  coal,"  tells  the  glacialist  that  such  depth  of  erosion  was 
not  accomplished  by  the  edge  of  a  lobe,  as  stated  at  the  beginning  of  the 
discussion  of  The  Pottsville  Anticlinal.  To  properly  value  the  surface 
and  deeper  parts  of  the  bed,  a  series  of  specimens  were  taken  at  Morea 
and  compared  with  a  few  at  York  Farm,  in  an  unglaciated  region,  and 
also  at  Ashland,  on  the  extreme  edge  of  glaciation;  but  where  the  ice- 
sheet  had  massed  against  a  high  ridge,  and  possessed  weight.  The 
following  is  a  description  of  the  samples,  and  below  are  the  analyses: 

1.  Morea,  sample  of  the  mealed  Anthracite,  dull  and  pasty,  %  inch  thick  of 
section  (2)  of  the  drift  sheet  above.     Two  samples  (a)  and  (b). 

2.  York  Farm  Colliery,  sample  of  the  "black  dirt"  on  outcrop,  (a)  and  (b). 

3.  Morea,  north  outcrop,  sample  (a)  surface  of  bench  1,  (b)  same,  60  feet  below 
surface.     Dip  of  north  outcrop  90°. 

4.  Morea,  same,  bench  2,  (a),  surface;  (b),  60  feet  below. 

5.  Morea,  same,  bench  3,  (a),  surface;  (b),  60  feet  below. 

6.  Morea,  same,  bench  4,  (a),  surface;  (b),  60  feet  below. 

7.  Morea,  south  outcrop,  top  bench,  (a)  surface;  (b),  3  inches  below;  (c),  25  feet 
below;  (d),  38  feet  below.     Dip  of  south  outcrop  50°. 

8.  Morea,  bottom  bench,  (a)  surface;  (b),  18  inches  below. 

9.  Morea,  glaciated  surface  beneath  section  (1),  above. 

10.  Morea,  second  section,  crushed  Anthracite  fragments  18  inches  thick. 

11.  Morea,  glaciated  coal  beneath  second  section,  from  which  the  mealed  Anthra- 
cite paste  %  inch  thick  (analysis  No.  1  just  above)  was  scraped. 

12.  Morea,  north  outcrop,  250  feet  below  surface. 

13.  York  Farm  Colliery,  Salem  Bed,  lower  bench,  dip  25°,  20  feet  from  surface. 

14.  York  Farm  Colliery,  Tunnel  Bed,  dip  24°,  80  feet  from  surface. 

15.  Ashland,  much  crushed  outcrop,  1  foot  from  surface. 

16.  Ashland,  same  bed,  8  feet  from  surface. 

17.  Ashland,  same  bed,  35  feet  from  surface. 

All  of  these  samples  except  (14)  are  from  the  Mammoth  (E)  Bed. 
The  highest  carbon  ratio  is  38.37,  given  by  the  polished  coal  taken  from 
under  the  drift  at  section  (2)  above.  The  paste  scraped  from  above  it 
is  mealed  Anthracite  and  not  black  dirt,  as  its  carbon  ratio  (11.18)  is 
very  little  less  than  the  hard  coal  taken  250  feet  below  the  surface  (sample 
12),  and  is  far  better  than  the  ratio  of  the  solid  bottom  bench  of  the 
south  outcrop  at  the  surface  (sample  8a,  ratio  0.98).  These  analyses 
were  made  by  Dr.  H.  E.  Kiefer.  Physical  tests  were  made  of  these 
samples  by  Dr.  J.  Barrell,  which  show  that  the  decay  is  preglacial.  He 
reported : 


BROAD  MOUNTAIN  DRIFT.    LOBE  NO.  2 


49 


1.  "Samples  18  inches  from  the  surface  are  as  strong  as  those  3  feet  from  that 
surface.     The  strongest  of  all  is  but  3^  inches  from  surface." 

2.  "Samples  near  the  surface  of  North  Crop  are  as  strong,  if  not  stronger  than 
those  at  a  depth  of  55  feet." 

3.  "Sample  No.  3  (No.  12  above)  taken  250  feet  below  surface  was  an  especially 
hard,  solid  piece  of  coal,  and  gave  fairly  uniform  results;  but  its  average  is  not  different 
from  that  of  the  more  fissile  samples  taken  at  the  North  Crop." 

"Although  enough  time  has  elapsed  to  give  the  surface  coals  (in  places)  a  dull 
appearance,  the  strength  has  not  been  seriously  affected." 

ANALYSES  OF  ANTHRACITE. 

In  the  following  analyses  the  first  column  represents  the  combined  moisture  and 
volatile  parts  (I) ;  the  second,  the  fixed  carbon  (II) ;  the  third,  the  ash,  (III) ;  the  fourth, 
the  total,  (IV);  the  fifth,  the  ratio  of  fixed  carbon  to  ash,  (V). 


Analyses 

I 

II 

III 

IV 

V 

la 

29.74 

64.51 

5.77 

100.02 

11.18 

b 

30.78 

63.35 

5.73 

100.16 

11.05 

2a 

45.76 

29.88 

24.36 

100.00 

1.23 

b 

44.22 

30.99 

24.79 

100.00 

1.23 

3a 

13.08 

82.42 

4.50 

100.00 

18.33 

b 

4.55 

93.02 

2.44 

100.00 

38.20 

4a 

14.11 

77.82 

8.07 

100.00 

9.64 

b 

5.30 

88.62 

6.08 

100.00 

14.65 

5a 

15.66 

67.17 

17.17 

100.00 

3.91 

b 

4.12 

86.76 

7.12 

100.00 

12.19 

6a 

13.01 

83.97 

3.02 

100.00 

27.75 

b 

5.20 

90.28 

4.52 

100.00 

19.99 

7a 

8.41 

88.39 

3.20 

100.00 

27.70 

b 

7.49 

89.87 

2.64 

100.00 

34.07 

c 

7.34 

87.19 

5.47 

100.00 

15.95 

d 

6.12 

89.90 

3.98 

100.00 

22.59 

8a 

36.73 

31.38 

31.90 

100.00 

0.98 

b 

11.13 

84.97 

3.90 

100.00 

21.77 

9 

19.45 

77.60 

2.95 

100.00 

23.45 

10 

31.34 

59.48 

9.18 

100.00 

6.48 

11 

14.17 

83.65 

2.18 

100.00 

38.37 

12 

4.97 

88.21 

6.82 

100.00 

12.93 

13 

8.91 

88.69 

2.40 

100.00 

37.03 

14 

9.60 

79.41 

11.00 

100.00 

7.22 

15 

3.51 

16 

8.65 

17 

12.58 

The  Western  Middle  Basin.— Its  eastern  rim  is  5  miles  northeast 
of  Morea,  and,  therefore,  completely  covered  by  No.  2.  Morea  is  on 
the  edge  of  its  high  southern  rim  of  Pottsville  conglomerate  overlooking 
Mahanoy  Basin.  Wetherill  Junction,  4J^  miles  southwest  of  Morea, 
has  an  elevation  of  1200  feet  above  ocean  level,  and  is  thus  300  feet  below 


50  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

Morea.  It  is  in  the  gap  in  Broad  Mountain  through  which  the  head- 
waters of  Schuylkill  River  flow  from  the  swamp  immediately  south  of 
Morea.  The  crest  of  Broad  Mountain  rises  to  1800,  and  is  thus  300  feet 
above  Morea  and  600  above  Wetherill  Junction.  The  boundary  of  the 
Attenuated  Border  has  been  drawn  to  St.  Glair,  2  miles  farther  south, 
though  it  is  probable  that-  the  boundary  covered  Pottsville.  The 
surficial  mantle  at  Port  Carbon  must  be  studied  where  it  is  not  masked 
by  culm. 

The  crest  of  Broad  Mountain  was  covered  by  No.  2  at  the  headwaters 
of  Silver  Brook,  3  miles  southeast  of  Morea.  Its  crest  west  of  the  gap 
at  Wetherill  Junction  (1800)  is  1%  miles  nearer  Morea  than  is  St.  Clair, 
and  but  300  feet  above  it.  It  is  probable  that  the  ice-tongue,  that  was 
thrust  down  towards  Pottsville  through  Broad  Mountain  Gap,  massed 
its  western  margin  high  up  on  the  flank  of  the  mountain,  if  it  did  not 
reach  its  crest;  as  the  great  weight  of  the  ice  at  Morea  indicates  a  thick- 
ness sufficient  to  overtop  the  mountain  by  more  than  the  300  feet  neces- 
sary to  cross,  plus  the  drop  of  50  feet  per  mile  for  the  distance  between. 
The  resultant  of  the  regional  trend  westward  to  Susquehanna  River  and 
that  southward  as  shown  by  the  movement  of  the  coal  flakes  in  the  drift 
would  pass  through  the  crest  of  Broad  Mountain  west  of  the  above  gap, 
and  thus  it  will  be  necessary  for  a  careful  study  of  its  crest  to  be  extended 
westward  from  the  border  of  the  red  shale  valley  on  its  northern  flank, 
opposite  Frackville,  where,  at  a  higher  elevation  than  the  crest  of  the 
Pottsville  ridge  forming  the  southern  high  border  of  Mahanoy  Basin, 
we  find  Pottsville  conglomerate  boulders  in  Pottsville  drift  as  at  Morea 
but  on  red  shale,  showing  the  bending  of  the  edge  of  the  ice-tongue  about 
the  gap,  which  is  1  mile  broad  at  the  1500-foot  contour. 

Mahanoy  Basin. — Outside  of  the  Pottsville  inner  rim  of  this  basin 
is  the  anticlinal  valley  (Mauch  Chunk)  of  Mahanoy  Creek  which  forks 
at  Barry  on  account  of  the  complete  erosion  of  the  formation:  the  left 
of  the  swallow-tail  reaching  Susquehanna  River  at  Millersburgh;  the 
right  reaching  the  same  where  Line  and  Little  mountains  join  about 
the  spoon-end  of  the  formation,  15  miles  farther  north.  Mahanoy 
Creek  flows  in  an  almost  straight  line  along  this  northern  fork  for  30 
miles  between  Frackville  and  the  gap  in  Line  Mountain  where  it  escapes 
southwestward  to  join  Susquehanna  River  at  Herndon.  This  red  shale 
valley  from  its  end  at  Frackville  to  the  gap  at  Locust  Dale  is  worthy  of 
careful  study,  both  to  find  whether  Broad  Mountain  crest  was  reached, 
and  whether  the  ice-sheet  did  more  than  place  its  southern  margin  astride 
the  Pottsville  rim  of  Mahanoy  Basin  as  far  west  as  the  gap  at  Locust 
Dale.  The  entire  Mahanoy  Basin  was  covered  by  ice,  as  shown  by 
numerous  sections  in  drift,  and  at  Frackville  that  margin  extended  2J^ 
miles  south  of  its  Pottsville  border.  The  eastern  end  of  Mahanoy  Creek 
Valley  is  plainly  covered  by  a  drift-sheet.  The  ice  moved  along  the  strike 


BROAD  MOUNTAIN  DRIFT.    LOBE  NO.  2  51 

of  the  formations,  and  the  sheet  soon  approximates  to  the  local  outcrop. 
There  was  no  opportunity  for  an  examination  of  sections  to  the  rock 
floor,  and  there  is  a  deep  surface  wash.  No  erratics  were  seen  between 
Gordon  and  Barry  where  the  swallow-tail  forking  occurs,  and  west  of 
Barry  the  red  shale  outcrops  without  a  cap. 

Ashland  Basin. — That  the  margin  of  the  ice  moved  astride  of  the 
Pottsville  rim  from  Frackville  is  shown  by  three  things:  the  smoothing 
of  the  crest;  the  crag-and-tail  drift  formation  at  its  end  at  Ashland  Gap, 
and  the  complete  crushing  of  the  coal  beds,  as  described  in  the  comparison 
of  coals  above.  This  is  checked  by  evidences  of  an  ice-tongue  thrust 
through  Ashland  Gap.  There  is  a  slight  red  shale  (Mauch  Chunk)  ridge 
immediately  south  of  and  against  the  Pottsville  one,  with  a  slight  trough 
between,  and  with  a  gap  in  it  east  of  Ashland  Gap.  Through  this  red 
shale  gap  a  stream  of  Pottsville  boulders  and  cobbles  was  poured  upon 
the  red  shale  plain  for  a  short  distance.  The  ice-margin  was  thus 
outside  of  the  Pottsville  ridge  at  Ashland  Gap,  as  well  as  2J^  miles 
outside  of  it  at  Frackville.  The  boundary  of  the  Attenuated  Border 
can  be  drawn  from  St.  Clair  so  as  to  pass  high  up  on  the  northern  flank 
of  Broad  Mountain,  and  thence  across  Mahanoy  Creek  Valley  to  the 
Big  Run  Gap  in  Mahanoy  (Pottsville)  Mountain  at  Locust  Dale.  This 
place  is  \Y±  miles  south  of  the  crest  of  Locust  Mountain  (1758)  and  1000 
feet  above  ocean  level.  Big  Run  drains  the  wedge-end  of  Ashland  Basin, 
which  extends  9  miles  west  of  that  place.  The  ice-sheet  passed  up  Big 
Run  and  ponded  its  water.  There  is  thus  an  abundance  of  drift  in  this 
wedge-end,  as  will  be  seen  below.  Ashland  Basin  was  entirely  covered 
by  the  ice. 

Locust  Mountain. — This  anticlinal  Pottsville  ridge  passes  southwest 
from  North  Mahanoy  Mountain  to  Mahanoy  Mountain,  joining  the 
latter  at  1800  feet  above  ocean  level  and  separating  the  Ashland  and 
Shamokin  Basins.  Mr.  J.  P.  Lesley  (Letter  of  transmission,  vol.  Z, 
p.  xli,  2d.  Geol.  Surv.  Pa.)  tells  of  Professor  Edouard  Desor  (1811-1882), 
the  Swiss  glacialist,  and  himself  finding  glacial  marks  on  the  crest  of 
Locust  Mountain  in  the  summer  of  1851.  This  overtops  Mahanoy 
Mountain  at  Big  Run  Gap  by  250  feet  and  is  but  1^  miles  north  of  it. 
To  cross  this  crest  (Locust  Mountain)  there  must  have  been  300  feet  of 
ice  on  it,  which  proves  the  covering  of  the  Ashland  wedge-end.  The 
railroad  from  Locust  Dale  passes  up  Big  Run  Valley  to  Locust  Summit. 
From  this  place  to  Locust  Gap,  in  Locust  Mountain,  is  a  continuous 
cutting  in  drift.  It  is  one  of  the  finest  exhibitions  in  Pennsylvania 
along  the  Attenuated  Border.  There  is,  however,  no  " attenuation" 
here,  as  the  drift  is  the  usual  sandy  clayless  body  including  abundant 
various  sandstones  and  conglomerate  masses.  The  exposure  just  east 
of  Locust  Summit  is  especially  fine.  From  Locust  Summit  (1340)  to 
Locust  Gap  is  a  fall  along  a  ponded  and  filled  valley  draining  northward 


52  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

into  Shamokin  Creek,  and  cuttings  in  a  thick  drift-sheet  are  numerous. 
It  carries  large  boulders  and  rests  of  a  glaciated  rock  floor. 

Shamokin  Basin. — The  outer  (Pocono)  border  of  this  is  Little  Moun- 
tain, which  is  an  extension  of  Nescopeck  Mountain,  which,  in  turn,  ex- 
tends the  Moosic-Pocono  barrier  across  the  ridge  at  Bear  Creek  Summit 
(2000)  and  sweeps  S.  50°  W.  for  36  miles  to  Susquehanna  River  as  the 
gradually  rising  border  of  the  Mauch  Chunk  valley  of  Nescopeck  Creek, 
and,  beyond  the  saddle  therein,  of  Scotch  Creek.  At  the  Nescopeck 
Creek  Gap  it  rises  900  feet  above  that  stream.  At  the  Susquehanna, 
near  Catawissa  it  turns  sharply  S.  45°  E.  for  9  miles  as  Catawissa  Moun- 
tain till  north  of  Raven  Run  it  returns  to  its  former  trend  by  a  short 
curve,  and  as  Little  Mountain  reaches  Susquehanna  River.  Its  average 
elevation  as  Nescopeck  Mountain  is  1750  (2000-1600) ;  as  Little  Moun- 
tain, 1300,  but  where  it  unites  with  Line  Mountain  (average  1300)  there 
is  a  knob  at  1500,  rising  1100  feet  in  one-half  mile  from  the  Susquehanna 
River  bank.  This  Pocono  barrier  separated  lobes  2  and  6.  The  sudden 
bend  at  Catawissa,  however,  enabled  No.  6  to  move  directly  southward, 
and  to  cross  Little  Mountain  along  its  whole  length  from  north  of  Raven 
Run  to  Susquehanna  River,  as  shown  by  the  drift-sheet  in  the  red  shale 
(Mauch  Chunk)  valley  between  it  and  the  inner  (Potts ville)  rim  of  Big 
Mountain.  East  of  Shamokin  Gap  this  sheet  is  at  least  30  feet  thick, 
as  shown  by  wells  sunk  into  it.  Whether  No.  6  crossed  Big  Mountain 
is  not  known.  The  evidences  of  ponding  in  the  valley  between  Locust 
Summit  and  Locust  Gap,  noted  above,  could  have  been  produced  by  the 
presence  of  No.  6  in  the  red  shale  valley  at  Shamokin  Gap,  as  Shamokin 
Creek  would  have  been  dammed  and  the  water  backed  to  its  source  so  as 
to  include  the  above  valley,  and  it  would  not  be  necessary  for  No.  6  to 
have  crossed  Big  Mountain. 

The  evidences  of  ponding  are  greater  north  of  Locust  Gap,  as  there 
is  a  swamp  extending  northeastward  to  Mount  Carmel  in  which  Shamokin 
Creek  rises.  The  evidences  of  glaciation  below  the  level  of  ponding, 
which  have  not  been  ascertained,  must  of  necessity  be  confused,  if  not 
submerged  by  the  water-laid  drift.  At  Excelsior,  3  miles  west  of  Locust 
Gap,  the  railroad  cutting  shows  the  rock  floor  planed  and  covered  by 
drift.  The  valley  is  narrow  here  and  obscured  by  culm.  Greenbank 
is  2J£  miles  west  of  Excelsior,  and  directly  north  of  the  junction  of  Locust 
and  Mahanoy  mountains  at  an  elevation  of  1800  feet  above  ocean  level. 
One  mile  east  of  Greenbank  there  is  another  exposure  of  drift  on  a 
glaciated  rock  floor.  There  are  two  sorts  of  drift  in  the  flood-plain,  the 
upper  is  stratified.  Unstratified  drift  is  found  55  feet  above  and  south 
of  Shamokin  Creek  in  Shamokin,  as  shown  in  Figure  23.  There  is  no 
southward  movement  of  the  ice  shown  by  coal  flakes,  and  thus  the  sheet 
seems  to  have  been  that  of  No.  2.  Outside  of  Shamokin  Gap  in  Big 
(Pottsville)  Mountain,  and  on  top  of  the  saddle  in  the  Mauch  Chunk 


BROAD  MOUNTAIN  DRIFT.    LOBE  NO.  2 


53 


valley  south  of  Trevorton,  Figure  24  shows  the  crossing  of  Little  Moun- 
tain (in  the  background)  by  No.  6  which  carried  the  Pocono  boulders 


FIG.  23. — Glaciated  coal  outcrop  and  drift  cap,  Shamokin,  Northumberland  Co. 


FIG.  24. — Pocono  cobbles  and  trash  carried  from  Little  Mountain  (background) 
across  Mauch  Chunk  valley  at  Trevorton  and  left  on  Pottsville,  Northumberland 
Co.  ' 

plentifully  scattered  over  the  surface,  and  found  in  the  drift,  from  the 
mountain  crest  across  the  valley  and  up  the  northern  flank  of  Big 


54  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

Mountain  where  the  camera  was  placed.  This  proves  the  crossing  of 
Little  Mountain  and  the  ability  of  the  ice-sheet  to  mass  against  Big 
Mountain.  Whether  it  crossed  the  latter  is  doubtful,  as  it  averaged  200 
feet  higher  than  Little  Mountain.  Where  it  met  Mahanoy  Mountain 
at  the  spoon-end  of  Shamokin  Basin  there  was  a  corresponding  knob  200 
feet  higher,  and  rising  to  1700  feet  above  ocean  level.  The  western  end 
of  this  basin  must  be  examined  carefully.  Immediately  below  this  knob, 
at  Hunter,  on  the  Mauch  Chunk  valley  is  a  drift-sheet  carrying  the  same 
dense,  white  Pocono  boulders.  Across  the  valley  to  the  southern  margin 
is  a  sandy  yellowish  drift  with  infrequent  Pocono  boulders.  As  there  was 
no  glacial  dam  here,  this  is  land-laid  drift,  and  evidently  from  No.  6.  The 
high  Pocono  rim  about  this  Mauch  Chunk  valley  of  Zerbey  Run  (Trevor- 
ton  to  Dornsife)  was  therefore  covered  by  the  eastern  margin  of  No.  6, 
and  there  was  thus  a  meeting  with  No.  2  at  the  end  of  this  region,  if  not 
farther  east  in  the  Shamokin  Basin.  Referring  again  to  the  tendency  of 
No.  2  to  gain  southing  at  Broad  Mountain  and  Ashland  gaps,  it  seems 
as  if  No.  6  may  have  pushed  No.  2  southward  by  crossing  the  Pocono 
crest  of  Nescopeck-Catawissa-Little  Mountain,  and  by  this  have  increased 
its  power  so  as  to  cross  Locust  Mountain  and  move  southward  through 
the  above  gaps.  The  boundary  of  the  Attenuated  Border  is  drawn 
through  Big  Run  Gap  at  Locust  Dale  so  as  to  include  the  wedge-end  of 
Ashland  Basin,  thence  over  Locust  Mountain  about  the  basin  of  the 
western  branch  of  Shamokin  Creek,  through  the  high  gap  in  Big  Moun- 
tain at  Trevorton,  thence  along  the  flank  of  the  latter  mountain  and  at 
the  base  of  its  high  knob  across  the  valley  of  Mahanoy  Creek  to  the 
Pocono  barrier  of  Line  Mountain,  where  it  sweeps  about  it  several 
hundred  feet  above  the  valley  floor,  and  passes  over  Little  Mountain 
east  of  the  knob,  and  thus  into  the  main  valley  of  Susquehanna  River. 
The  ability  to  cross  Little  Mountain  indicates  a  thickness  of  ice  sufficient 
to  place  the  glacial  surface  at  Sunbury  2100  feet  above  ocean  level. 


CHAPTER  VII 
SUSQUEHANNA  DRIFT.     LOBE  NO.  6 

The  St.  Lawrence-Black  River-Susquehanna  lobe  crossed  the  Black 
River  saddle,  the  Mohawk  trough  and  the  Pennsylvania  plateau  east  of 
Moosic  Mountain,  which  separated  it  from  No.  2  and  probably  kept  it 
from  crossing  into  the  Lackawanna  Anthracite  Basin,  as  the  Pocono  ridge 
from  Moosic  Mountain  southward  to  the  gap  at  Pittston  averaged 
over  2000  feet  above  ocean  level,  and  beyond  that  gap  was  but  1000 
feet  above  it.  No.  6  crossed  into  the  Wyoming  Valley  here  and 
moved  south  so  as  to  rest  against  Nescopeck  Mountain  and  extend  west- 


SUSQUEHANNA  DRIFT.    LOBE  NO.  6  55 

ward  to  the  highlands  (2300)  on  the  boundary  between  Wyoming  and 
Sullivan  counties.  The  trend  of  the  lobe  was  about  S.  30°  W.  here,  and 
thus  30°  nearer  south  than  No.  2,  with  an  increasing  pressure  against 
Nescopeck  Mountain,  which  enabled  it  to  cross  it,  as  will  be  seen,  and 
to  pass  south  far  enough  to  cross  Little  Mountain  as  described  imme- 
diately above.  It  extended  at  least  to  the  broad  saddle  at  McClure 
between  the  Middle  Creek  and  Juniata  basins,  and  at  the  left  a  tongue 
was  compressed  between  Shade  and  Jacks  mountains  (both  Oneida 
ridges),  while  the  right  margin  moved  along  and  against  the  Oneida 
zig-zag  between  White  Deer  and  Paddy  mountains,  after  coalescence 
with  the  left  margin  of  No.  7. 

The  outcrops  crossed  extend  from  the  Chemung  to  the  coal  until  past 
the  Wyoming  Valley.  Thence  to  the  McClure  saddle  they  are  between 
the  Oneida  and  the  Pocono.  This  brings  to  the  mixture  the  Lewistown 
limestone  and  Salina  shale,  which  distinguish  this  from  the  drift  of 
No.  2.  The  movement  with  the  Susquehanna  River  furnished  an  abun- 
dance of  rolled  gravel,  which  in  places  is  carried  over  the  highest  ridges. 
Much  of  the  valley  drift  is  the  overwash  from  the  great  moraine,  which 
crosses  the  river  at  Beachhaven,  42  miles  north  of  Little  Mountain  Knob. 
The  area  covered  by  No.  6  is  thus  divided: 

The  North  Branch. 

The  Main  Valley. 

Middle  Creek  Valley. 

Jacks  Mountain  and  Penns  Creek. 

The  North  Branch. — The  Berwick  gravels  have  been  described  (see 
preface  note,  D,  p.  180)  as  an  unstratified  clayey  drift  with  rolled  stones 
where  granite  and  anthracite  meet,  a  stratified  overwash,  and  a  cap  of 
unstratified  sand  with  iceberg  inclusions.  Figure  25  shows  Susquehanna 
gravel  carried  over  Nescopeck  Mountain  and  mixed  with  rolled  Pocono 
from  its  crest  and  angular  Mauch  Chunk  from  Scotch  Valley.  The 
mixture  is  on  the  slight  ridge  of  the  latter  formation  that  forms  a  continu- 
ation of  McCauleys  Mountain  at  Mountain  Grove  (1010  above  ocean 
\ level).  This  is  south  of  the  trough  of  Scotch  Valley,  2  miles  south  of  the 
crest  of  Nescopeck  Mountain,  and  6^/2  south  of  Beachhaven  where  the 
great  moraine  crosses  the  north  Branch  of  Susquehanna  River.  It  is 
also  directly  north  of  Frackville,  and  shows  that  a  pressure  southward 
was  exerted  on  No.  2  here  also.  It  is  thus  probable  that  No.  6  may  have 
coalesced  with  No.  2  over  the  last  3fc  miles  of  its  path. 

The  crossing  of  Little  Mountain  by  No.  6  has  been  noted  above.  The 
dropping  of  Susquehanna  gravels  behind  ridge  crests  has  been  mentioned 
in  chapter  four,  in  the  fifth  cause  for  the  approximation  of  drift  to  the 
local  outcrop.  Figures  26,  27  and  28  illustrate  the  passage  of  No.  6 
from  Susquehanna  River  to  Little  Mountain  when  once  past  the  Nesco- 
peck barrier.  The  first  shows  the  abundant  rolled  pieces  south  of  the 


56 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


hill-crest  2  miles  south  of  the  river  and  300  feet  above  it.     The  second 
the  scanty  gravel  on  the  hill-crest  6  miles  south  of  the  same,  and  just 


FIG.  25. — Pocono  drift  from  Nescopeck  Mountain  on  Mauch  Chunk  extension  of 
McCauleys  Mountain,  at  Mountain  Grove,  Luzerne  Co. 


FIG.  26. — Pocono  and  Pottsville  conglomerate  on  Catskill  at  hill-top  north  of  Rush- 
town,  Northumberland  Co.     (Gravels  from  Susquehanna  River.) 

north  of  and  225  feet  above  Shamokin  Creek.     The  large  cobble  is  rolled 
and  glaciated  Pocono.     The  third  is  on  the  same  road  as  the  other  two, 


SUSQUEHANNA  DRIFT.    LOBE  NO.  6 


57 


south  of  Shamokin  Creek  and  on  a  Hamilton  ridge-crest.     The  Susque- 
hanna  gravels  have  disappeared  and  the  semi-rolled  pieces  are  from 


FIG.  27. — Pocono  cobbles  on  Hamilton  on  ridge  north  of  Shamokin  Creek  at  Deiblers, 
Northumberland  Co.     (Showing  disappearance  of  Susquehanna  gravels.) 


FIG.  28. — Gravels  from  Shamokin  Creek  on  ridge-top  near  cross-road  to  Paxinos, 
south  side  of  ridge,  Northumberland  Co. 


Shamokin  Creek  bottom,  190  feet  (vertical)  below  and  1^  miles  to  the 
north. 


58  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

The  Main  Valley. — The  river  gravels  thus  carried  by  No.  6  are  abun- 
dant at  800  feet  above  Susquehanna  River  east  of  Sunbury,  but  die  out 
and  are  replaced  by  local  sorts  east  of  Selins  Grove.  At  low  levels  an 
overwash  underlies  sandy  clay  like  that  at  Berwick.  The  boundary  of 
the  Attenuated  Border  is  marked  across  Susquehanna  River  by  16  islands, 
on  two  of  which  the  Lewistown  Branch  of  Penna.  R.  R.  crosses  at  Selins 
Grove.  A  large  part  of  the  overwash  came  down  Penns  Creek,  and  is 
Oneida,  which  rock  is  not  found  along  the  North  Branch  of  the  river. 
Near  the  railroad  crossing  the  river  flows  on  a  rock  floor  of  Salina. 

Little  Mountain  Narrows. — The  knob  where  Line  and  Little  mountains 
meet  rises  to  1500,  or  1100  feet  above  the  Susquehanna  bank  %  mile  to 
the  east.  The  river  is  about  1  mile  broad  between  banks  at  the  junction 
of  the  north  and  west  branches.  At  the  narrows  it  is  3400  feet  between 
banks,  and  Hoover's  Island  occupies  1200  feet.  At  the  700-foot  contour 
the  breadth  is  1%  miles.  This  is  300  feet  above  the  water,  and  the  valley 
above  the  narrows  at  this  elevation  is  30  miles  broad  at  Sunbury,  and  15 
across  the  wedge-ends  of  Shade  and  Jacks  mountains.  The  saddle  at 
McClure,  in  Middle  Creek  Valley,  is  at  640  above  ocean  level.  The 
drainage  of  13,000  square  miles  of  Pennsylvania,  plus  all  of  New  York 
west  of  Delaware  water-shed  which  could  not  escape  westward,  all  of 
Canada  under  the  same  conditions,  all  of  the  ablation  of  the  main  trunk 
forced  through  the  Susquehanna  affluents  or  over  the  plateau,  and  all 
of  the  ablation  of  No.  6  and  the  northern  half  of  No.  2,  passed  through 
these  narrows.  The  berg-inclusions  in  the  Berwick  upper  sands,  and  in 
the  terrace  north  of  Rupert  narrows,  160  feet  above  the  river,  point  to 
extensive  clogging  by  bergs  there.  Similar  clogging  at  the  narrows  under 
consideration  laid  the  similar  cap  along  Penns  and  Middle  Creek  valleys, 
beneath  which  we  find  drift.  This  is  not  above  640.  The  drift  on  the 
hill  near  Sunbury,  800  feet  above  the  river  is  thus  land-laid,  also  the  still 
higher  drift  1000  feet  above  the  same>  where  No.  6  passed  to  cross  Little 
Mountain. 

Middle  Creek  Valley. — The  debouchment  is  curious,  being  through  a 
gorge  140  feet  broad  at  stream  level,  and  less  than  1000  feet  broad  75 
feet  above  it.  There  is  sudden  broadening  above  the  gorge  to  1800 
feet  at  stream  level,  and  to  3200  feet  at  the  1000-foot  contour.  The 
Susquehanna  flood-plain  runs  for  10  miles  up  the  valley  with  but  slight 
rise.  From  the  McClure  saddle  where  the  stream  rises,  to  within  8 
miles  of  its  mouth,  the  valley  is  6  miles  broad,  and  is  bordered  by  Oneida 
ridges,  Jacks  Mountain  (1540)  on  the  north  with  crest  900  feet  above  its 
trough  and  Shade  Mountain  rising  similarly  on  the  south.  A  slight 
Clinton  ridge  lies  next  to  and  apart  from  Jacks  Mountain.  The  valley 
floor  is  Salina  and  Hamilton.  The  Lewistown  Branch  of  Penna.  R.  R. 
passes  through  a  great  many  cuttings  in  drift  beneath  a  sandy  cap. 
The  drift  is  continuous  to  Adamsburg,  changing  from  gravel  to  angular 


SUSQUEHANNA  DRIFT.    LOBE  NO.  6 


59 


pieces  east  of  the  latter  station.  Between  this  place  and  Troxelville, 
however,  the  Middle  Creek  bottom  (Hamilton)  shows  abundant  rolled 
pieces  as  shown  in  Figure  29.  These  are  not  the  Susquehanna  gravels 
carried  west  of  Beaverton,  and  the  rolling  is  too  great  to  have  been 
formed  in  so  flat  a  stream  within  less  than  six  miles  of  its  source.  Besides 
the  stream  rilling  is  deep. 

There  is  a  surface  wash  between  the  McClure  saddle  and  Juniata 
River  at  Lewistown,  which  masks  whatever  is  beneath.  There  is  a  cut- 
ting on  the  saddle  of  considerable  depth  into  sandy  clay  including  small 
stones.  This  extends  through  the  town.  At  Raub's  Mills,  between 
Adamsburg  and  the  saddle  the  stones  are  larger,  and  there  may  be  a 


FIG.  29. — Bed  of  Middle  Creek  between  Adamsburg  and  Troxelville,  Synder  Co. 
Drift  of  Oneida  to  Salina  on  Hamilton. 

slight  moraine.  There  is  also  a  slight  gravel  ridge  running  from  the 
northern  end  of  Shade  Mountain  across  the  valley.  The  boundary  of 
the  Attenuated  Border  is  drawn  from  the  end  of  Little  Mountain  so  as 
to  enclose  Freemont  on  the  headwaters  of  Mahantango  Creek,  thence 
around  the  northern  end  of  Shade  Mountain  and  along  its  western  flank 
to  McClure,  where  it  curves  across  the  valley  to  the  eastern  flank  of  Jacks 
Mountain  west  of  Troxelville,  where  Oneida  boulders  have  been  carried 
across  the  Clinton  valley,  over  the  Clinton  ridge  of  Gold  Hill  and  left  on 
a  Salina  valley. 

Jacks  Mountain  and  Penns  Creek.— Troxelville  is  630;  Jacks  Moun- 
tain crest  on  the  road  thence  to  Glen  Iron  (Millmont),  1540.  It  is  an 
Oneida  anticlinal,  steeper  on  the  north  side,  and  with  a  sandy  cap  near 


60  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

the  crest.  This  is  absent  from  the  south  side.  A  brook  rises  near  the 
crest  and  flows  down  the  north  side  over  local  pieces  till  within  143  feet 
of  the  valley  where  it  is  full  of  gravel  from  Penns  Creek,  and  this  is 
carried  down  to  the  plain.  The  ice-sheet  massed  against  this  steep  flank, 
developed  a  shear  and  sent  the  clear  ice  and  sand  over  the  ridge.  This 
calls  for  a  thickness  of  1000  feet  over  Penns  Creek,  and  thus  agrees  with 
the  2100  feet  of  surface  elevation  at  Sunbury  mentioned  at  the  end  of 
chapter  six.  The  place  where  the  boundary  of  the  Attenuated  Border 
crossed  this  Mountain  is  not  known,  as  the  wilderness  is  unbroken,  and  no 
opportunities  were  found  for  search  westward.  It  must  have  been, 
however,  west  of  this  road  between  Troxelville  and  Glen  Iron. 

Penns  Creek. — This  has  a  delta  1  mile  broad,  and  the  Susquehanna 
flood-plain  runs  up  its  valley  for  20  miles  with  but  slight  rise.  The  valley 
was  covered  by  No.  6  from  the  mouth  to  its  gap  through  Paddy  Moun- 
tain, which  is  one  of  the  Oneida  zig-zags  of  the  border  between  the 
Susquehanna  Valley  and  the  many  trough  and  canoe-shaped  valleys  with 
Oneida  walls,  Martinsburg  rims  and  Cambro-Ordovician  floors  which  lie 
parallel  to  one  another  south  of  Bald  Eagle  Mountain.  This  zig-zag 
also  separated  No.  6  from  No.  7. 

•  At  Millmont  well-sections  gave  a  freshly  scoured  rock  floor  with  2 
feet  of  quicksand  upon  it,  covered,  in  order,  by  6  feet  of  assorted  stony 
gravel  free  from  sand,  2  feet  of  sand,  and  15  feet  of  sandy  silt.  The 
average  well  depth  is  25  feet.  From  Glen  Iron  station  westward  the 
railroad  cuttings  are  in  red  silt  including  glaciated  cobbles  and  boulders, 
angular  masses  and  slabs  of  local  rock — some  of  the  rolled  pieces  are  of 
good  size.  These  show  on  the  surface  also  all  the  way  westward  to 
Paddy  Mountain  Gap,  where  we  pass  out  of  the  area  covered  by  No.  6. 
The  boundary  of  the  Attenuated  Border  lies  along  the  northern  flank 
of  Jacks  Mountain  and  into  the  wedge-end  where  it  returns  as  Paddy 
Mountain,  so  as  to  include  Panther  Run  Valley. 


CHAPTER  VIII 
PLATEAU  DRIFT.     LOBE  NO.   7 

The  Ontario -Finger  Lake- Allegheny  Plateau  lobe  crossed  the  Erigan 
Valley  in  the  meridian  with  its  center-line  passing  through  the  Cayuga- 
Seneca-Lakes  pocket  and  the  channel  of  Susquehanna  River,  following 
the  latter  after  it  crossed  the  Pennsylvania  boundary  for  12  miles  and 
then  spread  fan-wise;  the  left  margin  passing  across  the  highlands  about 
Grant's  Lake  (2200-2400)  parallel  to  the  Wyoming-Sullivan  counties 
boundary  (about  S.  16°  W.)  and  coalescent  with  the  right  margin  of 
No.  6.  The  right  margin  of  No.  7  was  caught  in  the  broad  and  shallow 


PLATEAU  DRIFT.    LOBE  NO.  7  61 

troughs  of  the  plateau  and  turned  so  as  to  move  along  them  between  S. 
70°-80°  W.  With  the  first  portion  passed  the  water  forced  over  the 
plateau  which  could  not  escape  southward  through  the  Susquehanna 
trough,  as  it  turned  eastward  to  cross  the  plateau  crest  at  Tunkhannock, 
but  followed  the  ice  and  swept  the  plateau  clean,  so  that  where  the 
great  moraine  is  supposed  to  cross  the  trench  of  Lycoming  Creek  there  is 
no  vestage  of  it,  or  for  some  distance  east  or  west.  The  rocks  that  can 
be  expected  in  the  drift  of  this  lobe  will  not  vary,  between  the  Pennsyl- 
vania boundary  and  West  Branch  of  Susquehanna  River,  from  those  of 
No.  6  north  of  the  Wyoming  Basin.  In  the  valley  of  this  West  Branch 
the  rocks  down  to  the  Clinton  are  met  with,  and  south  of  Bald  Eagle 
Mountain  they  extend  down  to  the  Cambro-Ordovician  limestone;  but 
the  drift  there  is  mainly  from  the  Oneida  and  Medina  ridges — both  rocks 
much  softer  and  more  porous  than  those  on  the  Kittatinny  crest.  The 
Plateau  crests  are  mainly  Pennsylvanian  remnants  with  Pottsville  as 
the  rest  of  the  surface,  Mauch  Chunk  outcropping  thinly  along  the  walls 
of  river  trenches  and  Pocono  as  their  rock  floors  1000  feet  below  the 
plateau  level.  The  valleys  south  of  Bald  Eagle  Mountain  have,  with  one 
exception,  limestone  floors,  thin  Martinsburg  borders  and  high  Oneida 
rims;  the  exception  is  an  anticlinal  valley  in  Clinton.  The  drift  of  the 
left  margin  thus  extends  from  the  Cambro-Ordovician  limestone  to  the 
coal;  of  the  right,  is  confined  between  the  Pottsville  and  the  coal.  The 
area  covered  by  No.  7  is  thus  divided : 

Penns  Valley  to  Nittany  Valley. 
Sunbury  to  Keating. 
Sinnemahoning  Creek. 
Glacial  Lake  Lesley. 

Penns  Valley  to  Nittany  Valley. — The  former  is  the  region  where 
Penns  Creek  rises  and  forms  the  continuation  of  the  Attenuated  Border 
beyond  Jacks  Mountain  and  Panther  Run  Valley;  the  latter  is  the  largest 
and  most  western  of  the  canoe-shaped  valleys  south  of  Bald  Eagle  Moun- 
tain and  west  of  the  zig-zags  between  Paddy  and  White  Deer  Moun- 
tains— these  zig-zags  being  of  Oneida-Medina  ridges  that  surround  six 
valleys  east  of  Nittany  Valley.  Penns  is  swallow-tailed  at  the  ends ;  the 
next  north,  Brush  and  Sugar,  are  canoe-shaped;  still  farther  north  are 
three  hopper-shaped  ones  immediately  south  of  Bald  Eagle  Mountain; 
the  two  largest — Nippenose  and  Mosquito — having  limestone  floors. 
One  is  trenched  into  a  Clinton  anticlinal,  and  one  only  to  the  Martins- 
burg.  Two-thirds  of  the  area  is  Oneida-Medina,  and  the  drift  is  sand 
and  cobbles  from  this  ridge-former,  is  lighter  over  the  uplands  but  has 
the  usual  red  where  the  limestone  or  Martinsburg  outcrop. 

Drift  ends  in  Penns  Valley  at  Spring  Mills,  is  absent  over  the  limestone 
roll  to  Center  Hall,  State  College  and  Bellefonte.  The  east  end  of  Brush 
Valley  and  all  of  Sugar  and  the  more  northern  valleys  were  completely 


62  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

covered  by  ice.  The  boundary  is  drawn  over  Paddy  Mountain  to  Poe's 
Mills,  Coburn,  Spring  Mills,  Elk  Creek  Gap,  Madisonburg  (Brush  Valley), 
thence  over  the  Oneida  rim  to  include  the  western  end  of  Sugar  Valley 
and  pass  over  Big  Mountain  south  of  Big  Fishing  Creek  Gap,  if  not  south 
of  the  more  southern  one,  as  that  has  an  overload  delta  west  of  its  gap 
into  Nittany  Valley.  The  boundary  should  include  Hecla  Furnace. 
Across  Nittany  Valley  the  drift  is  hidden  by  Lesley  sands,  and  cuttings 
are  not  numerous.  It  is  found  beneath  the  above  sands  at  Huston, 
Figure  30.  This  valley  demands  considerable  study,  as  there  are  many 
overload  fan-cones  where  glacial  streams  discharged  into  Lake  Lesley. 

Sunbury  to  Keating. — The  striae  at  the  head  of  Little  Muncy  Creek 
bear  S.  5°  W.  and  show  the  trend  of  the  border  line  between  Nos.  6  and  7. 


FIG.  30. — Red  silt  including  Oneida  and  Martinsburg  on  Cambro-Ordovician  lime- 
stone, north  of  Huston,  Nittany  Valley,  Center  Co. 

The  valley  of  the  North  Branch  of  Susquehanna  River  is  deeply  filled 
between  Sunbury  and  Lock  Haven,  and  thence  to  Vail  in  Bald  Eagle 
Valley,  so  that  the  ridges  and  slight  elevations  rise  abruptly  like  islands 
from  the  level  Lesley  sands  and  clays.  The  presence  of  the  ice-sheet 
south  of  Bald  Eagle  Mountain  proves  that  this  ridge,  rising  1400  feet 
above  the  filled  valley  was  crossed  by  it.  This  indicates  a  glacial  sur- 
face rising  to  2100  feet,  which  is  the  elevation  calculated  for  Sunbury  in 
order  to  cross  Jacks  Mountain  by  No.  6.  Direct  proof  is  found  in  the 
drift  sheet  of  local  material  on  the  eroded  anticlinal  that  forms  the  north- 
ern flank  of  White  Deer  Mountain,  directly  south  of  Williamsport,  at 
1180  feet  above  ocean  level,  where  a  rolled  Medina  cobble  and  white 
quartz  pebble  were  found  after  passing  over  Bald  Eagle  Mountain,  across 


PLATEAU  DRIFT.    LOBE  NO.  7 


63 


the  intervening  valley  and  600  feet  upwards  on  the  northern  flank  of 
White  Deer  Mountain,  Figure  31.  This  thickness  is  not  excessive  for  the 
ice-sheet,  as  the  line  of  the  great  moraine  is  but  7  miles  north  of  the  place 
where  these  rolled  pieces  were  found;  but,  with  the  average  slope  of  No. 
6 — as  this  portion  of  No.  7,  on  the  margin  between  the  two,  should  follow 
that  slope — the  glacial  front  should  be  39  miles  south  of  Williamsport, 
if  that  front  rested  on  a  surface  900  feet  above  ocean  level.  Spring  Mills, 
where  the  rolled  drift  on  the  limestone  floor  ended,  is  40  miles  S.  45°  W. 
Lock  Haven. — The  filled  valley  turns  here  and  extends  up  that  of  Bald 
Eagle  Creek  to  the  Dix  saddle  and  the  Juniata  discharge  of  Lake  Lesley. 
Alleghany  Mountain  forms  the  western  border  of  this  valley,  and,  deeply 
trenched  into  its  Pennsylvanian-Mississippian  measures,  the  West 


FIG.  31. — Medina  cobble  and  quartz  pebble  from  drift  on  White  Deer  Mountain, 
south  of  Williamsport,  Lycoming  Co. 

Branch  of  Susquehanna  River  comes  from  the  northwest.  In  that  direc- 
tion the  surface  is  Pottsville  and  the  coal  forms  the  crests:  the  very  thin 
Mauch  Chunk  outcrops  half  way  down  the  vertical  walls  of  the  trenches 
in  which  the  rivers  run:  the  Pocono  forms  the  remainder  of  the  trench- 
walls  and  the  rock  floor.  Six  miles  north  of  Lock  Haven  and  over  700 
feet  above  it  (1500),  where  the  glacier  certainly  passed,  large  boulders  of 
sandstone  are  arranged  in  trains,  and  in  many  cases  are  forced  into  the 
putty-like  clay  even  with  the  surface.  These  are  4  feet  in  diameter  at 
times.  The  clay  includes  flakes  of  sandstone,  slabby  blocks  of  the  same, 
flakes  of  red  and  other  shales  of  lighter  (yellow)  color.  At  this  elevation 
the  ice-front  should  be  at  least  10  miles  to  the  south,  and  thus  4  south  of 
Lock  Haven. 


64  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

The  West  Branch. — Rattlesnake  Run  rises  4  miles  north  of  the  river 
and  above  Lake  Lesley  (1110).  Its  polished  rock  floor  is  crossed  by  a 
moraine  of  rolled  drift  of  all  sizes  that  did  not  come  up-hill  from  the  Sus- 
quehanna,  and  could  not  have  been  thus  thoroughly  rolled  in  the  short 
distance  from  the  source.  This  brings  the  ice  past  Haneyville,  20  miles 
southwest  of  the  great  moraine.  Several  runs  from  the  south,  between 
Hyners  and  Westport,  show  rolled  drift  in  their  beds,  and  thus  point  to 
ice  south  of  the  river.  Kettle  Creek  rises  near  the  great  moraine  at  Ger- 
mania.  Its  flood-plain  shows  gravel,  but  its  bottom  is  slabby.  The 
West  Branch  at  Keating  comes  from  the  Clearfield  region  to  meet  Sinne- 
mahoning  Creek  which  drains  the  southern  side  of  the  Pennsylvania 
plateau.  The  former  shows  signs  of  drift,  so  that  the  Attenuated  Border 
is  drawn  from  the  point  south  of  Mill  Hall  Gap  in  Bald  Eagle  Mountain 
so  as  to  pass  south  of  this  main  stream  to  Keating. 

Sinnemahoning  Creek. — This  flows  in  a  trench  parallel  to,  30  miles 
distant  from  and  1200  feet  below  the  great  moraine.  Bars  and  terraces 
occur  wherever  slack  water  obtained.  There  is  no  regular  filling  and 
their  tops  vary  spasmodically  between  15  and  120  feet  above  the  stream, 
jumping  within  a  few  miles  as  follows:  80,  100,  15,  14,  40,  80,  120.  The 
East  Branch  rises  3  miles  from  Coudersport  and  south  of  the  Allegheny 
watershed,  in  a  valley  where  18  feet  of  land-laid  drift  are  covered  by  a 
wash.  The  flood-plain  shows  drift,  but  the  stream-bottom  is  slabby. 
The  surface  of  the  plateau  about  the  trench  on  either  side  is  an  impassable 
wilderness  from  which  the  coal  and  lumber  has  been  removed  and  a 
tangled  underbrush  covers  everything.  There  are  few  roads  and  the  trench 
walls  are  sometimes  900  feet  high.  There  was  no  survey  of  the  surface. 

Bennets  Branch. — This  rises  against  the  Allegheny  watershed  at 
1678,  flows  east  and  joins  the  Sinnemahoning  at  Driftwood.  This  place 
is  below  the  water  level  of  Lake  Lesley  (1110-1130).  For  20  miles  west- 
ward— to  Medix— the  Pennsylvania  Railroad  passes  through  cuttings  in 
rolled  drift  from  100  to  1300  feet  long,  and  rising  from  8  to  20  feet  above 
the  track.  This  might  be  thought  to  be  due  to  the  ponding  of  Lake 
Lesley,  were  it  not  that  Medix  is  above  its  level.  The  discovery  by  Mr. 
Barrell  that  Bennets  Branch  reversed  its  current  during  glacial  times 
indicated  that  the  ice-sheet  crossed  Sinnemahoning  Creek  at  Driftwood. 
The  indications  of  reversal  are  the  prevalence  of  the  lower  parts  of  the 
affluents  of  the  stream  to  turn  against  the  present  current.  Johnson's 
Run,  from  the  south,  shows  the  presence  of  the  ice-sheet  over  its  old 
down-stream  mouth,  which  is  filled  with  drift,  until  a  new  channel  was 
trenched  through  the  rock  on  a  bend  up  stream. 

There  is  a  long  cutting  immediately  east  of  Medix  in  a  variety  of  drift. 
The  south  side  of  the  same  has  a  face  30  feet  high.  From  its  top  the  same 
gravel  can  be  carried  along  the  surface  in  an  upward  curve  between  1200- 
1500  feet  where  it  reaches  the  mountain  flank.  There  were  excavations 


PLATEAU  DRIFT.    LOBE  NO.  7  65 

sunk  in  places  to  test  theformation  below  track  level.  At  this  level  it  is 
a  decided  land-laid  drift  composed  of  the  old  surficial  mantle  mixed  with 
insufficient  vegetable  material  to  completely  reduce  the  ferric  salts.  Its 
base  is  a  bluish-brown  clay  including  rolled  and  sub-angular  boulders. 
Above  this  is  an  unstratified  body  of  local  flakes  with  larger  fragments, 
waterworn  and  subangular.  West  of  the  center  are  boulders  up  to  3  feet 
in  diameter.  At  the  western  end  this  changes  to  a  stratified  gravel. 
The  whole  is  a  moraine  showing  the  evidences  of  deforestation,  of  pond- 
ing and  of  an  overwash.  This  extends  to  the  south  as  shown  by  the 
presence  of  the  boulders  and  angular  fragments  in  the  bed  of  Medix  Run. 
One  mile  west  of  Medix  station  is  a  cutting  through  another  and  entirely 
different  formation,  700  feet  long,  angular  and  slabby,  without  rolled 
pieces  of  any  sort.  This  is  the  moraine  of  farthest  extension;  the  other  is 
one  of  retreat.  There  is  no  gravel  west  of  this  last,  but  there  are  two 
terraces  in  a  broad  and  filled  valley:  at  Weedville,  5  and  12  feet;  at  Pen- 
field,  Tyler  and  Winterburn,  3  and  5  feet.  The  flood-plain  is  composed 
of  flakes  of  Mauch  Chunk.  This  indicates  a  quiet  reversal.  It  is  not 
known  whether  the  discharge  was  into  Red  Bank  Creek  or  Clarion  River. 
The  former  shows  faint  indications  of  abnormal  flooding;  the  latter  shows 
a  deeply  trenched  and  broad  channel  into  the  rock  floor  with  a  gravel 
filling,  but  this  could  have  been  made  by  agencies  considered  later. 

Portage  Branch. — This  rises  on  the  summit  of  the  Pennsylvania  pla- 
teau and  is  joined  by  West  Creek  at  Emporium.  Its  office  as  a  discharge 
of  Glacial  Lake  Wright  will  be  described  in  chapter  ten.  It  was  crossed 
by  the  ice-sheet,  as  shown  by  ponded  drift  at  Shippen,  6  miles  below  the 
summit.  The  great  elevation  above  Lake  Lesley  is  evidence  that  the 
ponding  of  water  must  have  been  caused  by  a  local  obstruction. 

West  Creek. — This  stream  was  also  closed  so  as  to  raise  the  water  level 
several  hundred  feet  above  that  of  Lake  Lesley.  The  ice-sheet  came  to 
Emporium  to  accomplish  this.  The  rock  floor  of  this  stream  has  been 
trenched  so  that  the  affluents  come  in  at  so  much  higher  an  elevation 
that  they  seem  to  leap  into  the  valley.  At  Beechwood  (1240-1260)  is  a 
symmetrical  delta  through  which  the  stream  has  cut  a  channel  on  the 
up-stream  side  (as  reported  by  Mr.  Barrell).  This  indicates  a  reversal 
of  current  and  flow  over  the  West  Creek  Summit  (1696)  into  Elk  Creek, 
a  tributary  of  Clarion  River.  With  the  exception  of  an  occasional  boul- 
der in  the  mixture  the  rocks  are  local  and  angular.  In  the  adjoining 
streams  the  discoidal  gravel  carries  boulders.  The  deposits  are  either 
drift,  or  the  boulders  are  berg-carried.  There  are  no  deltas  as  high  as 
Rathbun  (1317).  West  Creek  flows  on  a  rock  floor,  but  there  is  gravel 
in  the  flood-plain  too  well  rolled  for  a  carriage  of  5  miles  from  the  source. 
The  hillside  cuttings  show  ordinary  wash,  as  in  the  Allegheny  region. 
At  the  summit  is  a  15-foot  cutting  in  silt  including  boulders.  This  is  6 
miles  north  of  Medix. 


66 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


Glacial  Lake  Lesley.  —  This  has  been  described  in  preface  note,  D  and 
F.     The  elevation  of  the  ponded  water  was  probably  1130.     The  col  at 


FIG.  32. — Outwash  from  Lake  Lesley,  showing  gradual  slackening  of  current,  one- 
quarter  mile  south  of  Vail,  Blair  Co. 


I  illlllll 


FIG.  33. — Outwash  from  Lake  Lesley,  south  of  saddle,  at  East  Tyrone,  Blair  Co. 

Dix  is  now  about  1110,  but  by  the  steeper  slope  on  the  Juniata  side  the 
watershed  has  been  pushed  north.  Figure  32  shows  the  sequence  of 
deposits  and  slackening  of  the  flow  over  the  col  a  short  distance  south  of 


PLATEAU  DRIFT.     LOBE  NO.  7 


67 


Vail.  The  iceberg  inclusions  are  seen  in  the  clay  cap.  Figure  33  shows 
the  overwash  near  the  bottom  of  the  southern  slope,  and  about  50  feet 
above  Little  Juniata  River  at  East  Tyrone. 

The  large  sausage-shaped  fan-cones  opposite  the  gaps  in  Bald  Eagle 
Mountain  which  project  across  the  valley  so  that  the  North  Branch  of 
Susquehanna  River  is  forced  to  make  great  loops  a  mile  or  more  to  the 
north,  and  off  the  Lewistown  limestone  floor,  in  order  to  pass  around 
them,  have  been  noted  in  both  papers  referred  to  in  the  above  preface 
note.  The  one  to  the  east  curves  with  the  present  drainage:  the  others 
against  it,  and  with  the  reversed  flow  by  which  Lake  Lesley  discharged 
the  drainage  of  5400  square  miles  over  the  col  at  Dix  into  Juniata  River. 
The  material  carried  therewith  is  shown  along  that  river,  and  a  very 


FIG.  34. — End  of  .fan-cone  from  Antis  Gap,  near  Jersey  Shore,  Lycoming  Co. 


small  part  of  it  remains  in  the  two  islands  at  the  mouth  of  the  stream  in 
Susquehanna  River — one  of  them  being  2  miles  long,  and  the  largest 
in  Pennsylvania. 

The  Jersey  Shore  fan-cone  was  originally  more  than  2  miles  long. 
Part  of  it  is  now  an  island  in  the  river,  2  miles  long  and  %  mile  broad. 
This  length  was  the  original  breadth  of  the  fan-cone,  whose  remnant 
now  is  more  than  1  mile  long,  }/±  mile  broad,  and  150-170  feet  above  the 
flood-plain.  Figure  34  shows  its  end,  Figure  35  its  structure.  The 
material  is  the  limestone  and  Martinsburg  slate  including  light-colored 
Oneida  and  Medina  cobbles. 

Figure  36  shows  a  section  on  the  south  side  of  Mill  Hall  Gap  in  Bald 
Eagle  Mountain.  At  the  bottom  is  land-laid  drift  covered  by  the  sandy 


68 


PENNSYLVANIA  GLACIATION.     FIRST  PHASE 


clay  of  Lake  Lesley.     Figure  37  is  a  cutting  in  the  fan-cone  outside  this 
gap,  which  also  turns  up  the  valley  with  the  reversed  flow.     Returning 


FIG.  35.^-Detail  of  cutting  in  fan-cone  from  Antis  Gap,  showing  rough  assortment  of 

strata. 


FIG.  36. — Section  of  fan-cone,  showing  drift  overlaid  by  unstratified  silt,  and  that 
by  slope-wash  from  Bald  Eagle  Mountain,  Mill  Hall  Gap,  Clinton  Co. 

to  Emporium  Junction,  Figure  38  shows  a  flat-topped  delta  formed  from 
the  material  in  the  floods  of  Lake  Wright  forced  over  the  Pennsylvania 


PLATEAU  DRIFT.    LOBE  NO.  7 


69 


plateau  through   the   Keating   Summit  trench   in   which   the   Portage 
Branch  of  Sinnemahoning  Creek  now  flows. 


FIG.  37. — Cutting  through  Mill  Hall  fan-cone,  Clinton  Co. 


FIG.  38. — Cutting  through  fag-end  of  delta,  Emporium  Junction,  Cameron  Co. 

It  remains  to  say  that  the  largest  boulders  found  along  the  Juniata 
River  are  3  feet  in  diameter;  the  average  size,  2  feet.  These  are  found 
in  the  top  sands,  indicating  the  presence  of  icebergs  and  cakes.  There 


70  PENNSYLVANIA  GLACIATION.     FIRST  PHASE 

must  have  been  a  deep  flow  over  the  col  at  Dix  to  carry  these  and  make 
a  stream  surface  80  feet  above  present  stream  level.  The  bergs  clogged 
the  narrows  so  that  the  flood-plain  of  Juniata  River  extends  several 
miles  up  their  valleys.  This  is  sufficiently  strong  to  be  noticeable  in  the 
topographical  quadrangles  of  the  region.  The  carriage  of  sporadic 
patches  of  gravel  100  feet  above  the  average  of  high  water  is  noted  in 
the  preface  references  above  noted,  and  was  caused  by  the  breaking  of 
the  ephemeral  cloggings  and  the  rush  of  the  wave  up  an  opposing  hillside. 


CHAPTER  IX 
HIGHLAND  DRIFT.     LOBE  NO.  8 

The  Ontario-Genesee-Sinnemahoning  lobe  moved  up  Genesee 
Valley  at  an  angle  of  thirty  degrees  with  the  trend  of  the  main  trunk 
of  the  ice-sheet.  At  Houghton  the  valley  makes  a  turn  of  50°,  so  that 
from  a  trend  of  S.  25°  W.  the  trough  slopes  upward  S.  20°  E.  On  the 
west  is  the  high  wall  mentioned  in  chapter  one,  which  turned  No.  8 
towards  the  highlands  of  Potter  County.  There  was  thus  a  steep  upward 
climb  for  this  lobe,  and  no  torrents  or  ridges  to  be  crossed  till  past  the 
line  of  the  great  moraine.  In  the  drift  of  the  mature  phase  we  find 
crystallines  in  abundance.  None  have  been  found  west  of  the  trench 
at  Keating  Summit,  as  far  as  known.  The  local  outcrops  west  of  this 
trench  are  thdse  of  the  plateau  to  the  east — from  Pocono  (trench  floor) 
to  coal  (plateau  crests).  The  discharge  of  water  over  the  plateau  has 
made  the  elimination  of  foreign  burden  complete,  and  the  inability  of 
the  right  margin  of  No,  8  to  mount  the  steep  bluff  of  Mount  Moriah  left 
the  basal  ice  and  its  burden  across  the  Allegheny  trough  at  Vandalia. 
The  drift-sheet  left  by  No.  8  was  very  thin  and  indefinite.  The  area 
it  covered  is  thus  divided: 

Clarion  River  Headwaters. 
Potter-McKean  County  Plateau. 

Clarion  River  Headwaters. — The  last  statement  about  West  Creek 
Summit  was  that  15  feet  of  silt  covered  the  divide.  Gravel  is  found  2 
miles  down  Elk  Creek  Valley  at  St.  Mary's,  20  feet  above  the  stream, 
and  occurs  for  some  distance  beyond,  and  sporadic  patches  of  the  same 
are  found  westward  to  Ridgway  on  Clarion  River.  The  East,  West 
and  Instanter  Branches  of  Clarion  River  are  full  of  rolled  and  angular 
gravel  in  bars,  terraces  and  flood-plains,  in  which  boulders  of  large  size 
occur.  These  slabby,  angular  and  rolled  deposits  rise  sometimes  be- 
tween 15  and  20  feet  above  the  river.  The  Clarion  is  peculiar  in  the  great 
number  of  small  feeders  that  rise  high  up  on  the  plateau,  and  head 
opposite  similar  small  affluents  of  Allegheny  River.  The  Clarion 


HIGHLAND  DRIFT.    LOBE  NO.  8  71 

affluents  leap  into  its  trough,  which  is  trenched  throughout  by  materials 
brought  by  No.  8. 

Potter-McKean  Plateau. — The  Johnsonburg  Branch  of  Pennsylvania 
Railroad  passes  up  East  Branch  of  Clarion  River  to  its  source  at  Clermont 
(2080)  where  it  crosses  the  plateau  crest  along  a  broad  and  shallow  trough 
to  the  Mill  Brook  branch  of  Potato  Creek.  The  region  is  smoothed  and 
the  surface  dotted  with  rounded  stones.  Mr.  Kiefer  reported  (1896) 
15  feet  of  gravel  in  a  cutting  south  of  the  town.  At  Wilcox,  on  the  West 
Branch,  a  drive-pipe  passed  through  a  stratified  outwash  of  glacial 
origin,  as  follows: 

Surface  soil  and  sandy  loam 5  feet. 

Loam  and  gravel 5 

Gravel  and  pebble 10 

Gravel  and  sand 5 

Gravel  and  pebble 5 

Gravel  and  sandrock 5 

Quicksand  and  pebble 5 

Fine  sand 3 

Total 43 

Well  drillers  call  sandless,  waterworn  gravel  "pebble."  This  indi- 
cates that  the  peculiar  sandless  gravel  of  the  Allegheny  Valley  about 
Warren  is  found  on  the  plateau  also. 

The  plateau  shows  the  usual  swampiness  which  is  an  evidence  of 
glaciation  on  high  levels.  Katrine  Pond  Swamp  (2300)  is  one  of  the 
largest  of  these  areas.  The  region  was  briefly  examined  along  the  lines 
of  railroads,  which  are  more  numerous  at  date  than  20  years  ago.  The 
principal  work  was  performed  in  connection  with  the  spreading  of  the 
margin  of  the  main  trunk  from  the  west.  One  of  the  evidences  of  the 
inability  of  No.  8  to  send  all  of  its  breadth  over  the  plateau  is  nicely 
shown  in  Mr.  Leverett's  map  (preface  note  A,  plate  iv).  The  basal  ice 
massed  against  the  bluff  south  of  Allegheny  River,  and  the  burdenless 
top  passed  onward  to  the  crest,  as  will  be  seen  later  in  describing  the 
attack  from  the  northwest.  This  ends  the  frontal  work  by  lobes  whose 
drift-sheets  can  be  distinguished.  The  parallelism  of  the  great  moraine 
and  the  boundary  of  the  Attenuated  Border  as  shown  in  the  frontispiece 
is  not  only  interesting,  but  seems  to  have  been  the  reults  of  depositions 
by  different  phases  of  the  same  lobes. 


72  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


CHAPTER  X 

SOUTHERN   MARGIN   OF  THE  MAIN  TRUNK.     FLUVIATILE 

DRIFT 

The  patch- work  stream  called  Allegheny  River  and  its  environment 
can  not  be  divided  into  areas  whose  drift-sheets  can  be  separated  and  dis- 
criminated, as  can  the  lobal  areas  of  the  state.  The  story  here  is  of 
ponding  on  a  massive  scale,  of  widely  spread  sediments,  of  similarity 
instead  of  discordance.  It  is  necessary  to  ascertain  the  causes  of  the 
utter  change  in  the  character  of  the  drift.  Premising  that  the  pre- 
glacial  arrangement  of  the  regional  drainage  of  Mr.  F.  Leverett  will  be 
followed,  with  the  exception  that  " Allegheny"  will  be  used  for  his  old 
Upper  Allegheny  System:  "Tionesta"  for  the  old  Middle  Allegheny 
System,  and  " Clarion"  for  the  Lower  Allegheny  System,  the  following 
subjects  will  be  considered: 

The  Geology  and  Present  Topography. 
The  Preglacial  Topography  and  the  Cols. 
The  Glacial  History: 

Glacial  Lake  Wright,  4  periods. 

Conewango  Slack  Water,  3  periods. 

Glacial  Lake  Leverett,  3  periods. 
The  Border  of  the  Ice-sheet. 

The  Geology  and  Present  Topography.  Geology. — The  vast  amount 
of  trenching  performed  in  connecting  the  separate  river  systems  makes 
it  necessary  to  understand  the  difference  between  the  rocks  of  the 
Pennsylvanian-Mississippian  formations  in  the  Anthracite  and  Bituminous 
portions  of  the  state.  In  the  latter  the  sandstones  are  porous,  soft  and 
so  water-soaked  as  to  form  a  huge  reservoir  where  water  can  be  obtained 
— even  on  top  of  the  hills — by  sinking  to  a  depth  of  100  feet.  In  a  region 
subjected  to  severe  cold  this  saturated  condition  aids  the  breaking-down 
of  rocks,  and  especially  along  the  lower  parts  of  the  canyons  in  which 
the  streams  flow,  as  there  the  reservoirs  discharge  through  seepage  springs 
at  water  level,  and  thus  tend  to  maintain  a  square  bottom  section  to  the 
canyon.  In  the  same  manner  this  tendency  to  disintegrate  under  the 
action  of  frost  helps  to  sharpen  the  spines  of  the  narrow  ridges  between 
adjacent  and  parallel  streams.  The  rocks  have  very  perfect  systems  of 
joints,  and  readily  break  into  cubes.  The  smaller  pieces  form  the 
boulders  which  average  2  feet  in  diameter  and  attain  a  maximum  of 
3  feet;  the  largest  are  known  as  components  of  the  "Rock  Cities"  which 
occur  in  the  region.  In  both  cases  the  results  are  due  to  glaciation;  fhe 
"Rock  Cities,"  to  the  settlement  of  the  stagnant  ice-sheet,  as  told  in 
the  beginning  of  chapter  two. 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  73 

Topography. — The  prominent  features  have  been  given  in  chapter 
one.  The  Salamanca  promontory  extends  10%  miles  north  of  the  state 
boundary  at  an  elevation  of  2200,  with  crests  up  to  2400.  In  places  its 
spine  is  less  than  250  feet  broad.  Its  end  drops,  in  %  mile,  820  feet  to 
the  filled  flood-plain,  and  1170  feet  to  the  rock  floor  of  the  Allegheny 
River.  The  drop  on  the  west  side  to  where  the  same  flood-plain  enters 
the  Big  Bend  trench  is  1000  feet.  On  its  east  side  is  a  drop  of  700  to 
the  flood-plain  of  Tunungwant  Creek,  which  is  carried  at  1500  feet  above 
ocean  level  one-third  of  its  distance  in  the  meridian  into  the  Cattaraugus- 
McKean  plateau.  At  Tarport  there  is  a  sudden  rise  to  the  crest  of  the 
latter.  East  of  the  Tuna  trench  is  an  extension  of  the  McKean  County 
plateau  to  the  Allgeheny  trench  at  Vandalia,  with  average  elevation 
200  feet  higher  than  that  of  the  Salamanca  promontory.  Its  highest 
summit  is  Mount  Moriah,  and  its  drop  is  greater  (900)  and  more  abrupt 
than  at  the  end  of  the  latter. 

Quaker  Ridge  extends  from  near  Kane  through  the  northwest  corner 
of  Warren  County  to  Chautauqua  County,  N.  Y.,  with  a  sharp  spine  that 
falls  gradually  to  the  northwest  till  it  disappears  beneath  the  trough 
filling  of  Conewango  Creek  at  Kennedy,  N.  Y.  (1300)— a  fall  of  800  feet. 
The  great  moraine  crosses  this  ridge  east  of  this  trough.  The  regional 
quadrangles  are  referred  to  for  the  details  of  the  present  drainage  system. 
Especial  attention  is  asked  for  the  one  giving  the  region  from  Franklin 
southward  to  include  Brandon,  Kennerdell,  the  filled  channels  north  of 
Egbert's  Hill,  between  Polk  and  Takitezy,  the  trench  south  of  the  for- 
mer, and  at  Fosters,  as  these  substantiate  the  arrangement  suggested  by 
Mr.  F.  Leverett,  Fig.  6,  p.  135,  preface  note  A.  For  McKean  County 
see  Mr.  Ashburner's  topographic  map,  vol.  R,  2d.  Geol.  Surv.,  Pa.. 

The  Preglacial  Topography  and  the  Cols. — The  three  profiles  between 
Erigan  Valley  and  the  Allegheny  trough  have  been  given  in  chapter  one, 
and  explain  the  continuity  of  the  high  wall  west  of  the  Genesee  Valley, 
the  rise  necessary  to  cover  the  plateau,  and  the  inability  of  a  lobe  west  of 
No.  8  to  reach  the  latter  by  a  frontal  attack.  No  lobe  could  pass  up  the 
old  Upper  Allegheny  Valley,  as  its  trend  was  at  but  a  slight  angle  with 
that  of  the  main  trunk  of  the  ice-sheet.  Any  movement  towards  the 
McKean  County  highlands  west  of  the  high  western  wall  of  Genesee 
Valley,  would  be  turned  into  the  impetus  favoring  motion  southwestward 
up  Erigan  Valley.  The  tendency  to  move  towards  those  highlands  was 
thus  at  right  angles  to  the  main  motion,  and,  instead  of  being  favored  by 
the  more  continuous  procession  towards  the  Illinois  boundary,  was  de- 
pendent almost  wholly  upon  the  increase  in  thickness  of  the  ice-sheet  over 
the  trough  in  Western  New  York. 

The  southern  part  of  the  region  to  be  considered  was  drained  by  the 
Tionesta  (old  Middle  Allegheny)  System.  Its  debouchment  upon  the 
Erigan  Valley  was  west  of  that  of  the  Upper  Allegheny,  and  the  closing  of 


74  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

its  valley  mouth  was  thus  subsequent  to  that  of  the  latter.  Once  past  the 
Pennsylvania  plateau  there  was  a  chance  for  a  lobe  to  turn  southward 
along  the  eastern  edge  of  Ohio.  The  position  of  the  Conewango  and 
Brokenstraw  mouths,  and  the  direction  of  their  discharges  are  unimpor- 
tant, as  is,  also,  the  ability  to  trace  any  of  the  buried  streams  of  the  region 
beneath  their  thick  drift-sheet.  These  lines  would  have  been  of  value 
had  there  been  the  slightest  attempt  of  the  great  streams  to  resume  their 
preglacial  base-levels.  The  elevation  of  the  ponded  water  was  sufficient 
to  disregard  watersheds,  to  trench  many  cols  and  passes  sufficiently  to 
afford  temporary  relief,  and  to  so  cut  down  others  as  to  completely  change 
the  drainage  systems  of  the  entire  region;  so  that  the  present  Allegheny 
River  is  formed  of  the  parts  of  eight  separate  streams  before  reaching 
the  preglacially  dominant  stream  of  the  region — the  Clarion.  The 
greatest  drop  in  the  Allegheny  floor  below  Warren  is  but  8  miles  above 
its  junction  with  the  Clarion.  It  leaps  into  that  deeply  trenched  stream, 
as  do  most  of  the  Clarion  affluents,  and  thus  shows  that  the  preglacially 
trenched  Clarion  base-level  has  but  recently  begun  its  movement  up 
the  younger  stream. 

Cols. — In  view  of  what  has  just  been  said,  the  cols  are  most  important 
in  an  estimate  of  where  and  how  the  work  was  done  that  formed  Alle- 
gheny River,  which  is  the  subject  of  this  part  of  the  discussion.  The  first 
and  most  important  consideration  is  the  manner  of  making  and  the  ease 
of  forming  cols  in  the  soft  and  porous  sandstones  and  shales  of  the  Miss- 
issippian-Pennsylvanian  measures.  The  stream  floors  have  thrust  their 
square-bottomed  heads  deeply  into  the  mass  of  the  Pennsylvania  plateau. 
Either  side  of  the  valley  has  a  somewhat  uniform  rise,  and  the  rock  floor 
maintains  a  uniform  grade  to  within  a  few  miles  of  the  source,  where  it 
becomes  a  parabolic  curve,  and  from  2  to  4  feeders  leap  into  it  from  the 
crest  of  the  plateau.  A  very  good  example  is  afforded  by  Potato  Creek, 
which  has  one  of  its  feeders  rising  in  Cameron  County.  The  stream  flows 
across  McKean  County  in  the  meridian  east  of  Mount  Moriah  to  join 
Allegheny  River.  The  fall  from  the  source  is  450  feet  for  the  first  2  miles; 
100  feet  for  the  second;  30  feet  for  the  third;  and  an  average  of  15  feet 
per  mile  for  several  miles.  There  is  a  similar  undercutting  at  the  side 
bottoms,  which  extends  upwards  to  form  the  thin  spines,  as  noted  in  the 
Salamanca  promontory.  Rice,  Limestone,  and  Red  House  Brooks  are 
trenched  into  the  mass  of  the  latter.  Between  the  first  two,  where  the 
country  road  crosses,  the  breadth  of  the  spine  at  2000  feet  is  250  feet. 
Between  the  first  and  last  the  spine  at  2250  feet  is  but  a  few  feet  broad; 
at  2000,  but  500  feet  broad.  The  Quaker  Ridge  spine  averages  between 
300  to  500  feet  thick  at  2000  feet,  and  but  200  feet  thick  at  2100  feet  for 
1  mile  on  either  side  of  the  Big  Bend  trench;  while  for  6  miles  the  average 
thickness  at  2000  feet  is  1700.  These  thin  spines  might  hold  quiet  water, 
but  waves  of  any  force  would  batter,  and  an  ice-sheet  of  any  weight,  crush 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  75 

such  soft  and  porous  walls  with  ease.  The  wrenching  away  of  the  crushed 
fragments  by  a  torrent,  or  the  battering  incident  to  the  passage  of  bergs 
and  laden  ice-cakes  would  without  difficulty  make  an  initial  cutting  of 
from  150  to  200  feet  in  depth,  sufficient  to  start  trenching  across  a  crushed 
spine. 

The  following  passes  and  cols  enter  more  or  less  into  the  glacial 
history : 

Keating  Summit.  Portage  trench  between  the  Allegheny  and  Sinnemahoning 
basins.  Top  of  col  at  beginning  of  trenching  unknown.  Top  of  plateau  2400. 
Bottom  of  trench  1878.  Cut  in  the  meridian  across  the  Potter  County  plateau, 
immediately  east  of  the  McKean  County  Line.  Twenty  miles  west  of  the  great 
moraine. 

Clermont.  Broad  and  shallow  pass,  with  floor  at  2068  between  the  East  Branch 
of  Clarion  River  and  Mill  Brook,  an  affluent  of  Potato  Creek  and  Allegheny  River. 
Twenty-eight  miles  west  of  the  great  moraine. 

Glad  Run.  A  shallow  pass  between  the  Allegheny  (Kinzua)  basin  and  West 
Branch  of  Clarion  River,  below  2100. 

Kane.  Broad  and  shallow  pass,  floor  2025,  between  the  Allegheny  (Kinzua) 
basin  and,  to  the  east,  the  West  Branch  of  Clarion  River;  to  the  west,  the  Tionesta 
River. 

Barnesville.  Trench,  1500-1300,  between  the  preglacial  Conewango  and  Tionesta 
basins. 

Thompsons.  Trench,  161,0-1000,  between  the  preglacial  Conewango  and  Tionesta 
basins.  The  upper  level  is  half  way  between  Mr.  CarlFs  "at  least  1800,"  and  Mr. 
Leverett's  "at  least  1220." 

Torpedo.  Untrenched  pass,  about  1550,  between  Brokenstraw  and  Oil  Creek 
basins.  This  is  between  Garland  and  Grand  Valley. 

Titusville.  1610 — rock  floor  unknown,  trench  filled,  between  preglacial  Upper 
and  Lower  Oil  Creek  basins. 

Fosters.  +1500 — filled  trench,  rock  floor  unknown,  between  preglacial  East 
and  West  Sandy  creeks. 

Foxburg.  Trench,  top  between  1480-1450.  Filled  bottom,  between  preglacial 
West  Sandy  Creek  and  Clarion  River.  Located  between  Foxburg  and  Emlenton, 
but  called  after  former. 

The  following  are  cut  across  Quaker  Ridge  between  the  filled  Cone- 
wango channel  (1300)  and  Big  Bend  trench,  which  last  is  included.  They 
afforded  a  discharge  between  glacial  Lake  Wright  and  the  Conewango 
Basin  at  Warren  during  the  passage  of  the  margin  of  the  ice-sheet  up  the 
spine  of  the  ridge.  When  it  is  remembered  that  the  great  moraine  rests 
across  that  spine,  east  of  the  filled  channel  at  Kennedy,  it  is  at  once  seen 
that  until  the  end  of  the  Wisconsin  period  there  was  a  clogging  of  the 
old  channel  of  sufficient  bulk  to  enforce  the  trenching  of  Big  Bend  col  to 
its  present  depth,  with  a  rock  floor  200  feet  below  the  filled  channel  at 
Kennedy,  and  a  filled  trench  with  surface  100  feet  below  the  same.  The 
following  are  arranged  in  their  order  from  west  to  east: 

Kennedy.     Broad  preglacial  channel  of  Conewango  Creek,  now  filled  to  1250. 
North  Bone  Run.     Trench.     Top  about  2000:  bottom,  1582.     Leads  from  Mud 
Run  on  the  Allegheny  side. 


76  PENNSYLVANIA  GLACIA7ION.    FIRST  PHASE 

Bone  Run.     Trench.     Top  about  2000:  bottom,    1566.     Leads  from  Cass   Run 

Storehouse  Run.  Shallow  pass,  floor  1925.  Leads  to  deep  trench  from  the  east 
bank  of  Conewango  Creek. 

Reynolds  Run.  Broad  and  swampy  pass,  floor  2020.  Leading  to  Ackley  Run. 
The  trench  at  the  bottom  is  cut  2%  miles  at  1500  feet  into  Quaker  Ridge. 

Big  Bend.  Trench.  Crest  marked  2154  on  plate  1,  vol.  Ill,  2d.  Geol.  Surv., 
Penna.  Today  the  sheer  walls  rise  to  2040  and  2060  on  the  two  sides.  The  rock 
floor  is  probably  1100,  as  shown  by  oil  wells,  and  the  filling  is  at  1200.  The  spine  of 
the  ridge  immediately  to  the  west  rises  to  an  average  of  2100  feet  above  ocean  level. 

Glacial  History.  Introduction. — Comparative  slopes  for  the  main 
trunk  and  the  various  glacial  lobes  were  obtained  in  chapter  two.  With 
the  elevation  of  8000  feet  above  ocean  level  for  Lake  St.  Peter  and  a  fall 
of  5.77  feet  per  mile,  the  elevation  at  a  point  where  a  normal  to  the  trend 
of  the  lobe  would  pass  through  the  Salamanca  promontory  would  be 
5000;  the  thickness  above  the  Erigan  rock  floor,  5400+ ;  over  the  Niagara 
promontory,  4400 +.  The  present  elevation  of  the  Wabash  watershed 
is  800.  A  drainage  exit  to  Ohio  River  lay  below  1000  feet.  The  average 
rise  to  the  plateau  from  Erigan  Valley  was  2600  feet;  to  submerge  the 
crests,  2900-3400.  It  is  evident  that  it  would  require  far  less  effort  to 
move  the  front  of  the  main  trunk  (300  feet  high)  towards  the  above 
watershed  than  to  turn  at  right  angles  and  rise  2000  feet  to  the  top  of  the 
high  wall  of  the  Allegheny  Valley.  The  same  reasoning  can  be  employed 
to  show  that  No.  8  did  not  force  water  over  the  higher  passes  from  the 
Genesee  ponding  until  late  in  the  glacial  history  of  the  First  Phase.  The 
aged-appearing  drift-sheet  of  Northwestern  Pennsylvania  is  thus  of 
necessity  much  younger  than  that  left  by  No.  3. 

The  calving  of  bergs  from  the  Ontario  rock  shelf  into  the  ponded  water 
in  Erigan  Valley  has  been  noted  in  chapter  one.  The  carriage  of  native 
copper  in  an  ice-cake  to  Warren  will  be  told  below.  Bergs  and  cakes  must 
have  come  down  Professor  Spencer's  Laurentian  River  with  this  metal. 
How  they  came  to  sail  across  the  slack  water  in  the  Conewango  Valley  is 
unimportant.  The  fact  remains  that  they  did  so,  and  they  carried  not 
only  this  metal,  but  Canadian  rocks  so  friable  that  they  would  have 
been  crushed  to  powder  if  incorporated  in  the  ice-sheet.  We  have  thus 
the  certainty  that  some  of  these  ice-cakes  managed  to  remain  unincor- 
porated with  that  sheet.  The  largest  bergs  could  enter  the  submerged 
mouth  of  the  old  Allegheny,  as  the  depth  of  water  was  greater  than  900 
feet — probably  950. 

Why  the  regional  fades  is  fluvial  is  told  in  chapter  three,  which  de- 
scribes the  work  of  the  torrent  in  the  marginal  canyon;  the  gradual  pushing 
of  this  trough  up  the  hillside;  the  levitation  of  the  silt  from  the  surficial 
mantle;  the  origin  of  the  heavy  drift-sheet  in  the  valleys;  the  washing 
of  ridge  crests;  the  formation,  in  fine,  of  Mr.  F.  Leverett's  " stony  till" 
(preface  note  A,  p.  223) .  The  order  and  succession  of  the  causes  which 
produced  these  will  now  be  considered. 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  77 

Glacial  Lake  Wright. — The  reason  for  this  name  is  given  in  chapter 
three.  Its  greatest  area  was  5000  square  miles:  its  elevation  varied 
between  800  and  2150  feet  above  ocean  level.  It  covered  the  Upper 
Allegheny,  Conewango  and  Brokenstraw  basins,  and  was  surrounded  by 
those  of  the  Genesee,  Sinnemahoning,  Clarion,  Tionesta  and  Upper  Oil 
Creek.  Its  bottom  was  crossed  by  the  great  moraine  at  Kennedy  and 
Vandalia,  and  by  the  boundary  of  the  First  Phase  at  Clarendon,  though 
the  last  place  was  not  included  in  its  area  when  that  boundary  was  laid. 
It  discharged  at  times  through  several  of  the  passes  and  trenches  of  the 
above  lists. 

Period  One  began  with  the  separation  of  Upper  Allegheny  Valley 
from  the  ponded  water  held  against  the  Wabash  watershed,  and  ended 
when  the  water  level  was  raised  to  1500  and  a  discharge  over  Barnesville 
col  began.  This  level  ponded  the  water  to  Port  Allegany,  N.  Y.  and 
the  Cuba  pass,  both  in  the  Allegheny  Valley;  to  above  Roystone  in  the 
Tionesta  Valley;  almost  to  the  Torpedo  pass  into  Grand  Valley,  and  to 
within  100  feet  of  the  col  at  Thompsons.  Warren,  Irvineton,  Glade, 
Stoneham,  Clarendon  were  submerged  over  300  feet.  The  discharge  was 
entirely  through  the  marginal  canyon  of  the  ice-sheet  as  it  was  spread 
higher  up  the  southern  margin  of  Erigan  Valley. 

The  deposits  were  of  three  kinds :  The  orogenic,  see  scheme,  always 
red,  and  found  as  slope- washes  and  beach  deposits;  the  gravels,  sands, 
and  clays  from  No.  8  discharged  through  Cuba  pass;  the  stony  gravel 
from  the  marginal  canyon.  The  first  and  third  were  continuous  and  will 
not  be  again  mentioned.  The  first  is  found  against  the  scoured  rock- 
floor  at  Stoneham,  Clarendon  and  Sheffield,  in  spots.  It  is  25  feet  thick 
at  State  Line,  and  8  at  Smethport.  There  was  no  distribution  of  the 
second  sort  till  the  next  period. 

Period  Two  begins  with  the  discharge  over  Barnesville  col  at  1500  and 
ends  with  the  discharge  over  the  Pennsylvania  plateau.  The  elevation 
of  Barnesville  col  is  indicated  as  above  1480  by  the  deposits  at  Clarendon 
at  a  later  period. 

Conewango  Valley  was  separated  from  Lake  Wright  during  this  period, 
and  its  history  will  be  considered  separately.  The  advent  of  the  glacial 
margin  and  its  gradual  movement  up  the  spine  of  Quaker  Ridge  developed 
discharges  over  that  spine  through  the  cols  in  the  second  list.  In  time  the 
level  of  the  Keating  col  was  reached  and  discharges  over  the  plateau 
began,  at  a  lower  elevation  than  the  col  at  Big  Bend,  and  all  secondary 
to  that  along  the  marginal  canyon,  wherever  that  may  have  been  situated. 
The  reversed  flow  up  the  Conewango  and  over  Barnesville  col  was  by  a 
current  that  never  exceeded  in  velocity  7  inches  per  second.  A  very 
good  example  of  the  sudden  broadening  of  valley  area  in  a  reversed  flow 
is  shown  by  measuring  the  distance  between  any  series  of  contour 
lines,  as  1500,  across  the  Conewango  Valley  from  State  Line  to  Watson. 


78  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

Remembering  that  this  valley  was  flooded  300  feet  deep,  and  that  a 
current  below  7  inches  per  second  passed  through  these  narrows  and 
suddenly  broadening  hollows  south  of  them,  we  can  understand  the 
sudden  checking  of  the  current  over  the  latter,  and  expect  the  deposits 
we  find  there,  while  none  exist  in  the  narrows.  The  Indian  Hollow  de- 
posits will  be  considered  later.  The  sudden  increase  in  area  there  to  twice 
that  of  the  narrows  immediately  above  gives  the  reason  for  their  deposi- 
tion. As  the  direction  of  the  current  has  been  maintained  to  the  present 
day  these  deposits  have  been  protected  from  scour  by  the  same  agencies 
that  caused  their  formation.  There  are  so  many  places  away  from  the 
subsequent  lines  of  scour,  as  the  cove  south  of  the  Oakland  Cemetery 
bar,  that  a  complete  valley  filling  must  of  necessity  have  left  equally  large 
deposits,  or,  at  best,  beach  lines,  to  show  the  continuity  of  that  filling. 
These  are  not  found  for  the  reason  that  the  current  which  brought,  and 
from  which  the  Indian  Hollow  deposits  were  dropped,  did  not  pass  across 
that  area,  but  moved  from  Warren  to  Glade  and  thence  to  Barnesville. 

Deposits. — (See  scheme  at  end  of  chapter  four.) 

Early  Fluviatile  Outwashes — A.  Conewango  Clay. — A  sticky  blued 
clay  mixed  with  vegetable  fragments  and  surrounding  large  piles  of  logs. 
This  is  found  continuously  from  Olean  to  State  Line,  Indian  Hollow3 
Glade,  Stoneham,  Clarendon,  and  the  northwest  edge  of  the  swamp  at 
Watson.  Thin  patches  are  found  at  Sheffield.  As  the  main  drainage  was 
through  the  marginal  canyon  this  must  have  come  through  Cuba  pass 
to  represent  the  deforestation  and  removal  of  the  surficial  mantle  in 
Genesee  Valley  by  No.  8.  It  is  Highland  material  levitated  and  distrib- 
uted by  Fluviatile  agents,  and  thus  becomes  the  lowest  of  their  deposits. 
At  Sheffield  it  shades  into  the  Orogenic  wash,  a  section  of  which  is  shown 
in  Figure  39.  Its  included  logs  and  chips  are  water-soaked  and  soft 
but  not  decayed.  Their  sharp  edges  and  splinters  resume  their  hardness, 
but  not  their  original  weight,  on  drying.  As  far  as  known  this  is  absent 
from  the  Brokenstraw  Valley — certainly  from  its  mouth.  It  is  100  feet 
thick  in  the  Conewango  Valley.  That  in  Tuna  Valley  is  from  the  same 
source,  but  of  a  later  period.  This  subject  will  be  more  fully  considered 
under  the  Conewango  Slack  Water. 

Period  Three  begins  with  the  flow  over  the  col  at  Keating  Summit 
and  ends  with  the  beginning  of  the  flow  over  Big  Bend  col.  The  varia- 
tion in  the  elevation  of  the  ponded  water  was  between  1878  and  2150 
above  ocean  level.  The  trenching  of  the  former  was  stopped  by  No.  8 
which  we  have  found  across  the  headwaters  of  Clarion  River,  and  thus 
across  this  trench.  A  flow  across  the  McKean  County  plateau  pro- 
duced results  similar  to  the  cloggings  in  the  Juniata  narrows,  as  the 
icebergs  hindered  the  flow  across  the  various  passes,  and  prevented 
decided  trenching.  There  was  now  a  reversal  of  current  in  Tuna  and 
Kinzua  valleys,  and  blued  clay  was  deposited,  which  fell  about  huge  log 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 


79 


piles  in  the  former,  and  is  100  feet  thick  12  miles  from  the  Allegheny. 
It  is  30  feet  thick  in  the  upper  part  of  Kinzua  Valley  at  1700  feet  above 
ocean  level.  This  march  of  No.  8  across  McKean  County  was  coincident 
with  its  crossing  the  high  western  wall  between  Genesse  Valley  and  the 
Allegheny  trench,  and  its  massing  against  the  bluffs  below  Mount 
Moriah.  The  elevation  of  ponding  is  shown  in  the  distribution  of  the 
drift  below  2000-2050,  the  washing  clean  of  the  small  areas  of  crest 
above  that  level,  and  especially  by  the  manner  in  which  the  drift  is 
thrust  in  slight  tongues  into  the  mouths  of  the  small  streams  that  flow 
down  from  that  mountain.  The  basal  ice  thus  checked,  there  was  the 
usual  shear,  and  the  clear  top  ice  passed  over  the  plateau  top,  carrying 
the  same  sands  and  mixing  them  with  the  small  local  fragments  on  top 


*•.,-.  te^::^w- 


FIG.  39. — Red  Orogenic  drift,  Sheffield,  Warren  Co. 

of  the  deposit  of  clay.  We  have  thus  two  kinds  of  drift  from  No.  8: 
that  from  the  southern  margin  rolled  and  mixed  with  angular  pieces,  as 
described  over  the  Clarion  headwaters:  found  at  Emporium  Junction 
over  100  feet  thick:  at  Clermont,  15:  at  Wilcox,  43,  etc.  Here  also  is  to 
be  placed  the  125  feet  of  red  gravel  at  Sheffield  from  the  flow  at  Kane. 
This  gravel  and  sand  are  interstratified  at  Wilcox.  This  is  Late  Highland 
drift,  and  it  overlaps  the  Early  Fluviatile  clay. 

Period  Four  begins  with  the  flow  over  Big  Bend  col  and  ends  with  the 
trenching  to  its  rock  floor,  now  100  feet  below  the  Allegheny  stream 
bottom— a  total  cutting  of  1000  feet.  The  margin  of  the  ice-sheet  was 
at  or  near  its  farthest  advance  at  the  beginning  of  this  period,  though 
it  was  by  no  means  near  its  boundary  farther  south. 


80  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

The  marginal  canyon  was  not  mentioned  in  the  discussion  of  the  last 
period,  though  it  is  evident  that  it  must  have  been  approaching  the  region, 
as  its  location  depended  upon  the  lowest  available  outlet  into  a  basin 
uncovered  by  ice,  and  as  the  margin  covered  the  lower  avenues  of  escape, 
it  sought  ever  the  lowest  of  those  that  remained.  The  trenching  of 
Keating  col  indicates  a  torrent,  but  one  swollen,  perhaps,  by  No.  8. 
It  is  possible  that  the  marginal  canyon  discharged  eastward  into  the 
Susquehanna  until  No.  8  crossed  the  Keating  trench,  as  Professor  Fair- 
child  has  shown  where  various  flows  passed  thither.  It  is  a  matter  of 
indifference,  however,  whether  all  the  marginal  flow  passed,  as  it  prob- 
ably did,  across  Big  Bend  col.  What  passed  was  sufficient  for  the  pur- 
pose, and  the  col  was  trenched.  When  we  remember  that  the  Kennedy 
channel  from  the  Upper  Allegheny  Valley  to  that  of  the  Conewango 
during  all  this  time  was  at  or  below  1250  feet  above  ocean  level,  we 
understand  that  the  ability  of  trench  Big  Bend  was  entirely  dependent 
upon  the  presence  of  the  glacial  margin  across  that  channel  and  the  spine 
of  Quaker  Ridge  to  the  col  at  Big  Bend.  That  the  ice  passed  beyond 
that  col  is  shown  by  the  moraine  at  Clarendon.  That  it  remained  at  or 
beyond  the  Kennedy  Channel  is  shown  by  the  depth  of  the  trenching,  as 
well  as  by  the  presence  of  the  great  moraine  between  it  and  Kennedy. 
The  level  of  the  ponding  in  Conewango  Valley  was  at  least  1600  at  this 
time.  There  would  be  a  fall  of  500  feet  between  the  Lake  Wright  and 
Conewango  levels.  This,  in  such  soft  and  porous  rocks,  and  down  a 
stream  with  a  parabolic  channel-head,  would  produce  a  water-fall  and 
rapids  sufficient  to  undercut  the  rock  over  which  the  fall  occurred. 
There  was  probably  no  very  long  duration  to  the  intense  first  period  of 
trenching. 

The  Deposits  from  No.  8  were  a  continuation  of  those  described  in  the 
previous  period.  To  these  must  be  added  the  drift  from  the  lateral 
margin  of  the  main  trunk.  In  the  Kinzua  Valley  we  find  the  blued  clay 
at  the  mouth  of  Glad  Run.  At  lower  levels  we  find  local  discoidal  gravel 
laid  in  foreset  bedding  and  dipping  downwards  against  the  present  stream, 
to  show  the  reversal  of  the  current.  The  surface  deposit  is  of  sand,  as. 
over  the  plateau  about  Kane  and  in  the  valley  of  Sugar  Run  which  adjoins 
to  the  north.  In  the  sand  are  fragments  of  sandstone  and  shale,  boulders 
of  sandstone  and  conglomerate,  and  masses  of  12  X  12  X  4  feet.  The 
shales  are  red  and  of  other  colors,  and  there  are  many  small  quartz  pebbles 
from  the  decayed  conglomerate.  These  are  all  from  local  outcrops,  and 
the  materials  differ  entirely  from  those  of  the  present  Allegheny  flood- 
plain,  which  abound  in  crystallines.  Although  there  is  a  continuation 
of  this  flood-plain  level  up  both  the  Kinzua  and  Sugar  Run  valleys,  there 
is  a  stoppage  of  the  crystalline  material.  In  the  valleys  north  of  Sugar 
Run  that  rise  in  the  Salamanca  promontory  this  is  not  the  case,  as  there 
the  crystallines  are  found  in  the  drift  as  well  as  in  the  flood-plain.  We 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  81 

also  find  crystallines  in  the  Conewango  Valley,  ^outh  of  the  Kinzua. 
This  and  Sugar  Run  are  peculiar  in  being  free  from  crystallines  in  the 
drift,  while  the  valleys  to  the  north  and  south  contain  them,  but  of 
different  kinds,  which  adds  to  the  variety.  The  tendency  of  the  drift 
to  become  local  has  made  the  difference.  The  movement  of  the  glacial 
margin  at  Warren  was  parallel  to  the  spine  of  Quaker  Ridge.  From  its 
summit  the  advancing  ice-wall  lay  across  the  Allegheny  trough  on  the 
north,  and  the  Conewango  trough  on  the  south.  It  scraped  upon  the 
Kinzua  and  Sugar  Run  outcrops  the  precisely  identical  rocks  from  the 
ridge:  into  the  valleys  to  the  north,  the  drift  already  washed  into  the  old 
Allegheny  trough:  into  the  Conewango,  and  to  Clarendon,  the  drift 
accumulated  in  the  old  Conewango.  As  for  what  is  in  the  present  Alle- 
gheny flood-plain  across  the  Kinzua  and  Sugar  Run  mouths,  it  was  not 
there  at  the  time,  as  Quaker  Ridge  was  intact:  Big  Bend  col,  untrenched, 
and  the  present  Allegheny  trough  then  lay  in  the  mass  of  the  ridge. 
Before  leaving  the  subject,  attention  must  be  called  to  two  wave-built 
terraces,  110  feet  apart,  reported  by  Mr.  Barrell,  with  elevations  ap- 
proximately (barom.)  1500  and  1600,  showing  sandy  beach  lines,  while 
between  them  the  valley  sides  are  rough  and  stony.  These  can  be  traced 
several  miles  from  the  valley  mouth  (Sugar  Run).  The  reddish  clayey 
silt  in  which  they  are  cut  carries  polished  sandstone  boulders  from  18 
inches  to  6  feet  in  diameter. 

Sculpturing. — There  was  a  stoppage  in  the  trenching  of  Big  Bend 
col  at  1500,  which  is  near  the  level  of  the  lower  terrace  just  mentioned. 
It  is  also  the  elevation  of  Port  Allegany,  N.  Y.,  where  the  broad,  flat  and 
filled  Allegheny  Valley  bottom — level  on  a  cross-section — changes  to 
one  V-shaped  and  narrowing,  with  the  angle  of  the  V  growing  sharper, 
and  the  stream  floor  rising.  The  slope  of  the  river  trough  from  the 
source  to  Port  Allegany  is  8.3  feet  per  mile:  thence  to  Olean,  1.8,  or  one- 
fifth  as  much.  This  1500-foot  valley  floor  remains  in  patches  in  the  race 
track  and  on  top  of  the  hill  at  Olean.  One  of  the  Salamanca  terraces  is 
near  that  elevation.  The  Cuba  pass  from  glacial  Lake  Genesee  is  2 
feet  below  it.  This  level  will  be  referred  to  when  we  consider  the  Cone- 
wango ponding.  The  remainder  of  the  history  of  Lake  Wright  is  so 
associated  with  the  latter,  that  we  will  consider  the  final  trenching  of 
Big  Bend  col  in  connection  with  it;  merely  premising  that  the  suction  and 
scour  of  the  current  flowing  through  the  trench  as  thus  far  sunk  had  not 
influenced  the  bottom  filling  of  the  old  Allegheny  trough.  That  occurred 
later. 

Conewango  Slack  Water. — Period  One  of  this  ponding  was  identical 
with  the  same  period  of  Lake  Wright,  as  stated  in  the  story  of  that 
lake. 

Period  Two  begins  with  the  discharge  of  a  small  portion  of  its  water 
over  the  Barnesville  col,  and  ends  with  the  closing  of  the  old  Conewango 


82  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

Valley  by  the  ice-sheet,  whose  margin  was  at  Clarendon.     It  comprised 
four  epochs : 

First  Epoch. — To  the  complete  separation  from  Lake  Wright. 

Second  Epoch. — From  the  closing  of  the  old  trough  at  Kennedy  by  the  ice-sheet, 
to  the  discharge  of  Lake  Wright  over  the  spine  of  Quaker  Ridge  above  2100. 

Third  Epoch. — From  the  closing  of  the  Quaker  Ridge  passes  to  the  discharge  of 
Lake  Wright  over  the  Pennsylvania  plateau. 

Fourth  Epoch. — From  the  discharge  over  the  plateau  to  the  closing  of  the  Cone- 
wango  channel  and  the  cessation  of  a  flow  from  its  ponded  water  over  Barnesville  col. 

During  the  first  two  the  bulk  of  the  ponded  water  was  discharged 
through  the  marginal  canyon,  and  but  a  small  volume  came  from  Warren 
to  Barnesville.  The  bulk  of  the  torrent  that  trenched  that  col  came  from 
Kane.  The  bergs  and  ice-cakes  escaped  through  the  marginal  canyon. 
The  approach  of  the  glacial  margin  brought  its  canyon  into  the  region. 
Wherever  it  discharged,  it  did  not  do  so  through  Brokenstraw  Valley. 
The  duration  of  the  second  epoch  must  have  been  considerable,  as  Bone 
and  North  Bone  trenches  were  probably  sunk  300  feet  each,  and  not 
together.  There  was  also  the  deep  trenching  of  the  heads  of  Ackley 
and  Hemlock  runs. 

We  now  come  to  the  flow  from  the  plateau  about  Kane  through  the 
affluents  of  the  old  Coriewango  (present  Tionesta)  source.  The  stoppage 
of  the  blued  clay  at  the  northwestern  edge  of  the  swamp  at  Watson  has 
been  mentioned.  Without  a  stronger  flow  from  the  east  that  clay  should 
have  been  spread  to  Barnesville:  it  stopped  4  miles  from  the  col.  Even 
after  the  glacial  margin  came  to  Clarendon  its  crystalline  and  local  rolled 
gravel  stopped  before  reaching  Watson,  and  5  miles  from  Barnesville. 
There  are  no  crystallines  in  the  Tionesta  below  that  place  till  we  reach 
the  bar  across  the  mouth,  produced  by  another  cause,  as  will  be  noted 
later.  From  Kane,  therefore,  came  the  125  feet  of  red  gravel  at  Sheffield, 
and  the  rest  of  the  burden  of  the  torrent  which  trenched  the  col. 

Deposits. — Under  this  heading  in  period  two  of  Lake  Wright  the  con- 
tinuous deposition  of  clay  was  stated  to  have  occurred  in  this  period  also, 
and  that  the  glacial  scheme  there  introduced  would  be  repeated  under 
the  present  heading. 

Early  Fluviatile  Outwashes — A.  Conewango  Clay. — The  scoured 
rock-floor  is  rarely  covered  with  orogenic  slope  wash  or  gravel.  Gener- 
ally in  the  Conewango,  Allegheny,  Tuna  valleys  the  sticky  blued  clay 
is  against  it  with  logs  and  wood  fragments.  On  the  north  side  of  Indian 
Hollow  the  writer  took  a  piece  of  hemlock  from  it  1  foot  above  the  scoured 
rock  floor,  and  20  feet  below  the  surface.  Oil  wells  show  that  this 
scoured  floor  slopes  toward  and  beneath  the  stream  floor,  and  that  before 
any  deposition  took  place  there  was  a  deep  cove  behind  the  shoulder  of 
the  projection  from  Quaker  Ridge.  Clay  also  caps  the  rock  cutting  of 
the  railroad  opposite  Glade,  and  drive  pipes  show  it  beneath  the  gravels 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  83 

there.  It  does  not  underlie  the  Allegheny  flood-plain,  <and  is  absent 
beneath  the  Brokenstraw  deposits.  It  varies  from  100  to  200  feet  at 
Stoneham,  as  will  be  noted  later.  At  Clarendon  it  is  100  feet  thick 
against  the  rock  floor  at  a  point  48  feet  above  and  to  one  side  of  the  trough 
bottom.  A  little  farther  south,  and  where  the  torrent  from  Kane  during 
the  beginning  of  the  ponding  sent  its  burden,  it  is  130  feet  thick,  but 
overlies  102  feet  of  red  orogenic  gravel.  At  Tiona  the  Kane  and  Warren 
currents  met,  and  the  blued  clay  is  intermingled  with  a  flaky  local  wash. 
Like  the  Indian  Hollow  cove  this  Clarendon  area  is  where  there  is  a  sudden 
broadening  of  the  valley  section  to  thrice  the  area  of  the  narrows  imme- 
diately to  the  north.  This  clay  for  a  time  was  carried  to  Sheffield.  In 
one  place  it  is  2  inches  thick:  in  another,  10  feet.  It  rests  on  red  clay, 
either  clean  or  mixed  with  red  gravel. 

It  remains  to  consider  whether  there  was  a  complete  filling  of  clay 
over  the  valley  at  Warren.  Its  absence  from  beneath  the  present  flood- 
plain  and  from  beneath  the  Brokenstraw  gravels  proves  that  if  originally 
deposited  in  those  places  it  was  completely  removed  before  their  deposi- 
tion. Figure  41,  to  which  reference  will  be  made,  goes  farther  and  proves 
that  it  was  never  generally  deposited,  and  that  these  classical  deposits 
at  Indian  Hollow  and  Clarendon,  like  those  at  Brandon  and  Kennerdell, 
were  deposited  in  the  " holes"  in  a  reversed  flow. 

Early  Fluviatile  Outwashes — B.  Lower  Indian  Hollow  Sands. — 
These  fine  sands  are  60  feet  thick  (drive-pipe  section)  and  dip  in  foreset 
strata  southward  17°.  After  deposition  they  were  smoothed  along  a 
horizontal  plane  1316  feet  above  ocean  level.  They  are  divided  into: 

1.  Quicksands,  assorted  and  free  from  clay,  lying  on  the  clay  or  the  rock  floor. 

2.  Interstratified  fine  sands  and  rock  meal  with  lenticules  of  clay  (both  clean 
and  sandy).     The  total  thickness  of  these  and  the  underlying  quicksands  and  clay 
is  160  feet  at  a  point  from  60  to  75  feet  above  the  rock  floor  of  the  valley  trough. 
The  average  dip  varies  between  20°  of  the  top  beds  and  the  gradually  decreasing  values 
of  the  underlying  beds. 

Figure  40  shows  the  east  side  of  the  sand  workings.  The  dark  stratum 
gives  the  dip.  The  soft  appearance  of  the  surface  indicates  the  fineness 
of  the  sands.  The  oil  well  in  the  background  afforded  the  section  of 
the  formations  here.  The  workings  have  considerable  breadth.  On 
the  opposite  side  Figure  41  shows  conclusively  that  there  was  no  uniform 
filling  of  the  valley  with  sand,  but  that  the  strata  were  dropped  in  the 
slackened  water  behind  the  projection  from  Quaker  Ridge.  On  com- 
paring the  strata  here  and  in  the  preceding  figure  it  is  evident  that  the 
latter  (40)  shows  an  area  away  from  the  scour  of  the  current.  The  narrow 
dark  strata  run  across  the  face  of  the  working  with  little  diminution  of 
thickness,  and  the  conditions  of  deposition  were  the  same  on  the  right  and 
left  of  the  figure.  Figure  41,  on  the  contrary,  shows  a  spot  just  on  the 
edge  of  the  line  of  scour.  Each  bed  thins  out  towards  the  left,  where 


84 


PENNSYLVANIA  GLACIATION.     FIRST  PHASE 


it  comes  within  the  area  of  the  latter.  In  other  words  there  were  two 
areas  at  the  time:  one  of  deposition  in  Indian  Hollow:  the  other  of  scour 
along  the  Conewango  channel  and  over  the  hillside  above  Warren,  where 


FIG.  40. — Lower  Indian  Hollow  sands,  east  side,  Warren  Co. 


'    FIG.  41. — Lower  Indian  Hollow  sands,  west  side,  Warren  Co. 

the  rock  floor  has  been  scrubbed.  To  settle  the  question  as  to  the  time 
when  this  deposit  was  sculptured  and  smoothed  to  its  present  contour, 
Leverett  Clay  with  its  iceberg  burden  caps  the  whole,  and  tells  us  that  as 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 


85 


we  see  this  section  today,  so  it  appeared  before  the  water  level  had  sunk 
below  the  top  of  these  sands. 


FIG.  42. — Clay  lenticule  with  iceberg  burden,  in  Lower  Indian  Hollow  sands, 

Warren  Co. 


FIG.  43. — Native  Copper  nugget,  clay  lenticule,  Lower  Indian  Hollow  sands, 

Warren  Co. 


Figure  42  shows  a  14-inch  lenticule  of  clay  6  feet  long,  at  1285,  carry- 
ing fragments  dropped  from  bergs,  among  which  was  the  nugget  of  native 


86 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


copper  of  Figure  43.  This  last  was  covered  with  a  film  of  oxide  ^2 
of  an  inch  thick.  A  shovelfull  of  the  lenticule  and  inclusions  showed  that 
the  latter  formed  but  one  per  cent.  The  foreign  rolled  pieces  were  the 


FIG.  44. — Upper  Indian  Hollow  sands,  Warren  Co. 


FIG.  45. — Detail  of  plunge  and  flow  stratum,  Upper  Indian  Hollow  sands,  Warren  Co. 

same  proportion  of  the  burden.  Of  the  pieces  over  J^  inch  mesh  11  per 
cent,  were  rolled.  Here  again  there  is  an  approximation  to  local  angular 
material. 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 


87 


Upper  Indian  Hollow  Sands. — This  series  of  coarse  sands  and  fine 
gravels  (J4  inch)  is  20  feet  thick,  and  laid  in  wavy  strata  nearly  horizontal 
(Figure  44).  Fine  gravels  are  interstratified  in  thin  layers.  At  1321 
is  a  bed  between  horizontal  strata,  with  plunge-and-flow  foreset  bedding 
dipping  north,  or  against  the  dip  of  the  other  beds,  as,  Figure  45  if  the  suck 
of  the  marginal  canyon  had  obtained  during  its  deposition.  The  top  of  the 
series  is  1336  above  ocean  level.  The  particles  are  fresh  and  free  from 
rusting.  The  same  series  of  blued  clay,  sands  and  fine  gravels  is  found  at 
Clarendon,  but  at  different  elevations,  the  top  of  the  sands  being  1443, 
or  107  feet  above  the  Indian  Hollow  top.  This  is  another  proof  that  there 
was  no  even  filling  of  the  valleys  during  this  period.  Had  there  been 
such  a  filling,  or  had  it  been  continuous,  there  would  have  been  a  connec- 


FIG.  46. — Clarendon  gravels  on  top  of  Upper  Indian  Hollow  sands,  East  Warren, 

Warren  Co. 

tion  between  Clarendon  and  Indian  Hollow  shown  by  the  slopes  of  the 
strata  along  a  uniform  dip. 

Middle  Fluviatile  Outwash — Clarendon  Gravels. — About  Warren 
these  are  found  below  1500  feet  above  ocean  level.  As  their  connection 
with  the  underlying  beds  is  best  studied  at  Indian  Hollow,  we  will 
examine  their  section  and  arrangement  there.  Figure  46  shows  the 
eastern  face  in  the  summer  of  1897.  The  oil  well  on  the  extreme  left  is 
the  one  shown  in  Figure  40,  with  base  at  1336,  which  is  the  elevation  of 
the  bottom  of  these  rusty  gravels.  The  top  of  the  cutting  rises  to  1396. 
Their  highest  point  as  a  continuous  body  is  1488  upon  the  shoulder  of 
the  ridge  2300  feet  distant.  Sporadic  patches  are  found  higher  up. 
The  height  of  the  face  is  60  feet.  The  thickness  is  20  feet  700  feet 


88  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

up  the  slope.  The  foreset  dip  of  17°  is  shown  in  Professor  Wright's 
Ice  Age  in  North  America,  5th  ed.,  1911,  Fig.  55,  where  the  clean  sand 
stratum  is  shown,  similar  to  one  at  Clarendon,  thus  showing  the  same 
succession  of  outwashes.  These  gravels  were  sculptured  to  their  present 
contour  during  the  ponding  of  the  Conewango,  as  shown  by  the  capping 
of  the  Leverett  Clay.  There  was  thus  no  general  valley  filling  of  gravels. 

They  are  found  in  the  basins  of  Hook's  River,  Dutchman's  Run,  and 
about  Glade  and  Clarendon.  At  the  last  place  they  are  of  three  varieties, 
and  in  three  belts  trending  N.  38°  E.  That  to  the  southeast  rises  8  feet 
above  the  swamp,  and  is  inconsequential.  There  is  a  railroad  cutting 
629  feet  long  through  the  middle  one,  and  at  1480  the  sides  rise  5  and  8 
feet  above  the  track.  The  station  and  platform  are  on  this.  The  third 
ridge  is  660  feet  northwest  of  the  middle  one,  and  extends  over  the  rail- 
road crest  to  Stoneham.  The  highest  point  of  continuous  drift  in  this 
ridge  is  1515.52,  but  sporadic  patches  are  found  higher.  The  greatest 
thickness  thus  far  known  is  71  feet,  overlying  stratified  sands.  The  front 
contains  almost  all  of  the  foreign  and  crystalline  rocks:  the  middle  is 
subangular  and  local,  with  the  rolled  pieces  decreasing  from  front  to 
rear,  and  a  minute  inspection  necessary  for  their  detection  on  the  sur- 
face: the  rear  (northwest)  resembles  orogenic  drift.  The  margin  rested 
here  long  enough  to  bring  up  the  retarded  basal  burden,  or  the  foreigners 
may  have  been  pushed  ahead  in  an  accumulation  of  ice-cakes.  If  so, 
these  were  incorporated  in  the  margin  and  not  floating — otherwise  we 
should  find  their  burden  dropped  along  the  channel  to  Barnesville.  The 
stoppage  of  these  gravels  at  Clarendon  tells  us  that  the  marginal  canyon 
did  not  pass  to  Barnesville,  and  that  the  torrent  from  Kane  still  was 
sufficiently  strong  to  push  back  whatever  came  from  Clarendon.  The 
original  thickness  of  gravel  at  the  latter  place  may  have  been  greater, 
as  will  be  considered  later. 

Of  the  same  period,  but  different  in  character  are  the  gravels  of  the 
bar  opposite  Irvineton,  from,  and  at  the  mouth  of  Brokenstraw  Creek. 
In  them  are  well-polished  pebbles  and  cobbles  of  pink  and  white  quart zite, 
much  rolled  Pocono,  fossiliferous  Catskill  and  a  few  crystallines.  These 
are  in  loam  mingled  with  local  material.  The  surface  is  covered  with 
Pocono  cobbles.  The  proportion  of  crystallines  is  smaller  than  at  Claren- 
don, and  there  are  boulders  several  feet  in  diameter.  At  milepost  227 
(P.  R.  R.)  there  is  a  gravel  deposit  of  similar  character  with  foreset 
bedding  dipping  towards  Warren,  and  underlying  the  flood-plain  gravels. 
There  are  no  indications  of  a  flow  over  Thompsons  col  at  this  time. 

Period  Three  begins  with  the  closing  of  the  Clarendon  channel,  and 
ends  with  the  trenching  of  Thompsons  col  to  its  present  rock  floor.  It 
must  be  remembered  that  the  bottom  of  the  trench  in  Barnesville  col  was 
about  1450  when  this  closing  took  place.  The  present  level  of  its  trench 
(rock  floor)  is  1300.  The  trenching  of  this  150  feet  has  thus  no  connection 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  89 

with  the  ponding  in  Conewango  Valley.  There  has  been  a  subsequent 
flooding  and  reduction  of  water  level,  as  this  trench  is  filled  60  feet  and 
there  are  two  terraces  between  which  the  present  stream  flows.  There  is 
thus  a  considerable  history  of  operations  that  took  place  during  this 
period  outside  of  the  Conewango  Valley,  and  in  what  will  hereafter  be  a 
part  of  the  Tionesta  (old  Middle  Allegheny)  system. 

Drainage. — After  the  stoppage  of  the  discharge  to  Barnesville  another 
and  higher  exit  became  necessary.  The  level  of  ponding  about  Titusville 
is  1610.64:  the  col  at  Thompsons  was  slightly  higher:  that  at  Torpedo, 
100  feet  lower.  Grand  Valley  was  thus  flooded  when  the  water  rose  to 
the  Titusville  col,  and  the  ponding  extended  down  the  Upper  Oil  Creek 
Valley.  The  higher  elevation  of  Thompsons  col  is  inferred  from  the  find- 
ing of  slack  water  evidences  south  of  Oakland  Cemetery  above  1610.64. 
There  seem  to  have  been  three  epochs  of  drainage: 

1.  Discharge  through  Grand  Valley  and  over  Titusville  col. 

2.  Closing  of  the  above  by  ice-margin,  and  discharge  over  Thompsons  col. 

3.  Trenching  of  Thompsons  col  to  present  level. 

In  all  of  these  there  was  never  sufficient  lowering  of  the  water  level  to 
bring  the  Torpedo  pass  or  the  drift-sheet  in  Grand  Valley  within  the 
line  of  scour.  During  the  first  of  these,  Grand  Valley  received  a  levitated 
deposit :  during  the  second  the  outwash  drift  from  the  ice  was  laid  down : 
in  the  third  both  cols  were  not  trenched  sufficiently  to  permit  scour  in 
this  valley  before  the  stagnant  ice  was  removed.  We  have,  thus  this 
oldest  of  the  drifts  of  the  region  with  its  original  irregular  surface. 

The  third  epoch  was  correlated  with  the  end  of  the  last  period  of 
glacial  Lake  Wright.  Whether  it  was  with  the  period  of  deposition  of 
Leverett  Clay  is  unknown,  as  all  of  these  valleys  were  again  flooded  to 
1500  when  the  level  of  Lake  Leverett  rose  suddenly  to  that  elevation  at 
the  time  the  ice-sheet  closed  the  mouth  of  West  Sandy  Creek  and  forced 
the  discharge  over  the  col  at  Fosters. 

It  remains  to  consider  whether  the  Clarendon  gravels  were  not  origi- 
nally of  greater  thickness.  The  stagnant  ice  probably  remained  for 
some  time  at  Clarendon.  If  it  did  not,  why  was  there  no  return  to  a  flow 
over  Barnesville  col,  as  the  present  elevation  of  gravels  at  Clarendon  is 
but  1513.32?  There  was  a  continuity  of  life  in  the  ice,  as  witness  its 
arrival  afterwards  at  Titusville,  and  still  later  at  Franklin  and  Foxburg. 
There  was  once  as  great  a  filling,  and  of  the  same  gravels,  in  Hook's 
River  basin,  but  only  the  traces  remain.  There  is  the  same  gravel  at 
Stoneham  as  at  Clarendon,  and  in  a  continuous  sheet,  but  while  it  rests 
on  sands  at  Clarendon,  it  has  been  dropped  on  the  underlying  clay  at 
Stoneham.  Now  the  highest  point  of  the  present  gravel  deposit  is  be- 
tween the  two  places.  It  looks,  therefore,  as  if  the  loss  of  100  feet  of 
underlying  sands  at  the  latter  place  had  taken  away  100  feet  of  eleva- 
tion of  gravel  from  the  apex,  and  that  its  original  elevation  was  about 


90  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

1600  feet.  This  would  show  why  a  head  of  100  feet  of  ponded  water 
about  Warren  and  above  the  present  top  of  the  gravels,  was  unable  to 
force  a  way  towards  Barnesville,  and  by  so  doing  distribute  the  crystal- 
lines towards  that  place,  and  into  Tionesta  River.  There  was  a  strong 
agent  at  work  which  had  no  trouble  in  removing  stagnant  ice,  but  when 
it  did  so  Thompsons  col  was  trenched  below  1500. 

Middle  Fluviatile  Drift — Land  Laid. — This  varies  with  the  local 
outcrop,  and  some  of  its  varieties  will  be  described  in  locating  the  bound- 
ary of  the  Attenuated  Border.  In  all  cases  there  has  been  an  insistence 
upon  finding  a  crystalline  piece  in  a  deposit  above  the  regional  ponding. 
This  limited  the  chances  and  made  them  far  apart  in  the  north.  In 
the  south  where  nearly  the  whole  of  the  glaciated  area  was  submerged 
the  chances  of  discovery  were  fewer.  Below  Foxburg  there  is  a  general 
submergence. 

Late  Fluviatile — Reworking  of  Old  Gravels. — The  shapes  of  the 
river  troughs,  the  fall  of  500  feet  from  Lake  Wright  to  the  Conewango 
level,  and  the  thin  and  soft  character  of  the  Quaker  Ridge  spine  at 
Big  Bend  have  been  described,  with  the  chance  of  undercutting  at  the 
fall.  It  is  probable  that  during  its  erosion  Thompsons  col  was  likewise 
trenched,  so  that  the  fall  of  the  level  of  the  ponded  water  in  Conewango 
Valley  kept  pace  with  that  in  Lake  Wright,  especially  as  in  addition  to 
the  flow  over  Big  Bend  col  there  was  added  the  accumulations  of  the 
Conewango  and  Brokenstraw  vallej^s.  The  first  effect  of  the  Big  Bend 
torrent  was  the  clearing  away  of  the  stagnant  ice  from  the  col  to  Glade, 
Warren,  Irvineton  and  Thompsons  col.  This  would  form  a  canyon 
with  ice  walls  between  which  the  torrent  would  flow.  The  clearance 
would  begin  at  the  top,  and  would  be  in  a  straight  line.  As  it  worked 
downwards  it  would  cut  into  and  remove  projections  from  the  valley 
sides.  In  this  manner  1000  feet  or  more  of  the  western  end  of  the  ridge 
between  Morrison  and  Ott  runs  has  been  removed,  and  from  1500  feet 
to  half  a  mile  from  the  one  between  the  latter  and  the  old  channel  of 
Brokenstraw  Creek,  where  it  turned  north  to  join  the  Conewango. 
This  cutting  is  well  shown  along  the  railroad  opposite  Glade.  The 
northern  end  of  the  ridge  points  its  wedge  toward  Warren  to  deflect 
subsequent  currents  from  the  deposit  behind  it  against  the  hillside  north- 
west of  Warren,  where,  below  the  1500  foot  contour  half  a  mile  has  been 
cut  away. 

The  clearance  of  the  gravels  from  Hook's  River  occurred  at  this  time, 
as  did  those  in  the  present  Allegheny  channel  from  Glade  westward. 
Dutchman's  Run  was  also  cleared  of  gravel,  but,  when  the  gravel  was 
removed,  the  underlying  sands  were  exposed,  made  quick  by  the  water 
and  run  out  as  far  as  Stoneham,  leaving  the  dense  clay,  and  dropping 
upon  it  the  gravels  beyond  the  influence  of  the  scour.  For  example, 
300  yards  east  of  the  P.  R.  R.  station  at  Stoneham  the  rock  floor  is  at 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 


91 


1115  with  210  feet  of  blued  Ccnewango  Clay  on  it.  At  the  foot  of  Bald 
Hill  are  130  feet  of  this  on  erogenic  gravel.  Nearer  Clarendon  30  feet  of 
gravel  remain  above  100  feet  of  clay.  The  sands  are  gone  completely. 
We  are  now  in  a  position  to  conclude  that  when  this  dropping  of  gravels 
occurred,  and  this  clearance  of  ice  from  the  channel  took  place,  that 
Thompsons  col  had  been  trenched  below  1500  feet,  or  there  would  have 
been  a  return  of  the  Conewango  discharge  over  Barnesville  col.  This 
brings  the  following  deposits  within  the  Late  Fluviatile  Period,  and  at  a 
time  long  after  the  formation  of  the  Clarendon  gravels. 

Early  Big  Bend  Gravels. — These  were  dropped  in  the  broadening  of 
the  ice  canyon  beyond  the  most  western  of  the  wedges  above  described, 
and  where  the  old  Brokenstraw  channel  lay,  in  a  long  bar  which  is  thrust 


FIG.  47. — Early  Big  Bend  gravels,  Oakland  bar,  South  Warren,  Warren  Co. 

with  gradually  diminishing  elevation  across  the  plain,  and  on  which 
Oakland  Cemetery  is  now  located,  the  end  of  which  is  shown  in  Figure  47. 
The  light  streaks  above  the  top  of  the  corn  field  are  the  end  of  the  terrace- 
like  bar  of  the  Middle  and  Late  Big  Bend  gravels.  This  gives  an  excellent 
idea  of  the  great  difference  in  the  elevations  of  the  two  formations.  Still 
lower  is  the  Allegheny  flood-plain.  Warren  is  in  the  left  distance.  The 
bar  is  similar  in  formation  to  those  in  lakes  Packer  and  Lesley.  It  is 
foreset  bedded,  shaped  during  the  prevalence  of  slack  water,  and  capped 
by  Leverett  clay.  The  figure  shows  that  it  is  not  a  wash  from  the  hillside, 
as  it  stands  away  from  it.  Its  crystallines  are  those  of  Clarendon  and 
Indian  Hollow  with  a  larger  proportion  of  local  material.  This  proves 
that  the  torrent  through  Big  Bend  was  not  yet  sufficiently  lowered  to 
scour  the  old  Kinzua-Allegheny  filling. 


92  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

Middle  Big  Bend  Gravels. — The  stagnant  ice  was  cleared  from  nearly 
the  whole  of  the  Conewango  valley.  There  was  a  sculpturing  of  the 
various  deposits  and  of  the  northern  side  of  the  Oakland  Cemetery  bar  as 
the  current  was  permitted  to  pass  to  the  north  of  it.  The  level  of  the 
water  fell  and  the  stream  through  Big  Bend  col  passed  into  shallower 
water,  where  the  sudden  broadening  west  of  Glade  checked  the  current. 
The  burden  of  the  discharge  from  Lake  Wright  changed  with  the  lowering 
col,  and  now  consisted  of  the  filling  of  the  old  Allegheny  Valley,  which 
formed  a  lower  and  broader  terrace  bar  hanging  to  the  southern  side  of 
the  present  valley  at  a  lower  level  than  the  one  dropped  in  the  last  period, 


FIG.  4&.— Middle  and  Late  Big  Bend  gravels,  South  Warren  terrace-bar,  Warren  Co 

and  of  entirely  different  materials.  Figure  48  gives  a  working  face  and  a 
fresh  section.  The  portion  beneath  the  conglomerated  top  belongs  to 
this  period:  that  top  to  the  next  one,  and  the  thick  clay  that  has  been 
cleared  from  the  shelf  on  top  is  iheLeverett  clay.  The  camera  is  150  feet 
from  the  face,  the  height  of  which  can  be  inferred  from  the  gravel  cars. 
The  boulders  are  mainly  from  the  top  clay,  and  show  iceberg  action.  The 
cobbles  and  boulders  are  far  larger  and  more  numerous  than  in  the 
Clarendon  gravels.  The  following  divisions  are  shown  in  the  figure, 
taken  in  1897: 

Middle  Big  Bend  Gravels 

A.  Coarse  gravel.     5  ft.     No  clay;  little  sand;  wavy  strata,  horizontal  to  slight 
foreset  dip  westward.     Depth  unknown;  pebbles  up  to  3  inches  diameter. 

B.  Lenticular  sandy  streaks;  wavy  strata  parallel  to  (A);  3  to  4  feet  thick. 

C.  Foreset  beds  of  assorted  pebbles;  dip  17°;  10  to  12  feet  thick;  smoothed  along 
a  horizontal  plane  about  20  feet  above  track  level.     UNCONFORMITY. 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  93 

Late  Big  Bend  Gravels 

Unassorted  gravels,  sandy  and  carrying  big  boulders;  18  to  20  feet:  foreset  bed- 
ding; dip  17°.  Top  smoothed  to  horizontal  plane. 

A  sample  from  (C)  was  washed  and  screened  to  3  sizes:  over  one-half 
inch,  one-fourth  to  one-half  inch,  less  than  one-fourth  inch.  Of  the  first, 
hand-picked,  less  than  one  per  cent,  were  crystallines.  There  were  110 
sandstones,  74  shales  and  19  limestones.  Of  the  second,  there  were  3.6 
per  cent,  of  crystallines — all  angular  pieces  of  black  syenite.  Of  the  third, 


FIG.  49. — Clastics  from  South  Warren  terrace-bar,  showing  mixture  of  decayed  and 
fresh  pieces  of  same  formation. 

there  were  20  per  cent,  of  crystallines.  This  tells  the  story  of  preglacially 
aged  crystallines  comminuted  in  the  rearrangement,  as  in  their  fresh  state 
they  are  far  harder  and  denser  than  the  local  elastics. 

Preglacial  decay  is  shown  in  Figures  49  and  50:  the  former  elastics, 
the  latter  crystallines  from  this  terrace.  The  large  slabs  in  49  are  from 
the  old  surficial  mantle  near  the  outcrop,  and  are  not  only  more  angular 
and  porous  than  the  fresh  rock,  but  their  calcite  fossils  have  been  almost, 
entirely  leached  away.  The  rolled  pieces  from  the  same  formation  occur 
next  them  in  the  formation,  have  been  exposed  to  the  same  weathering 
since  deposition,  and  are  still  hard,  dense,  and  with  polished  calcite 
fossils.  In  50  the  cobble  under  the  arrow  was  from  the  surficial  mantle, 
had  a  decayed  crust,  was  glaciated  till  the  fresh  white  nucleus  showed  on 
one  side.  Similar  ones  have  been  found  at  Clarendon.  Here  also  decay 
preceded  rolling.  Figure  51  shows  the  end  of  the  bar  cut  through  by  the 


94 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


country  road.     The  dashed  line  shows  the  form  before  the  cutting.     The 
capping  of  Leverett  clay  is  seen  on  the  farther  side  of  the  road  to  show  that 


FIG.  50. — Crystallines  from  South  Warren  terrace-bar,  showing  mixture  of  de- 
cayed and  fresh  pieces.  Cobble  under  arrow  has  fresh  (white)  nucleus  exposed  by 
rolling. 


FIG.  51. — Western  end  of  South  Warren  terrace-bar,  showing  shaping  before  deposi- 
tion of  Leverett  clay. 

the  sculpturing  occurred  before  its  deposition.     It  is  sandier  here  than  in 
48,  and  the  sand  is  freer  from  iceberg  burden. 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  95 

Glacial  Lake  Leverett. — The  reason  for  this  name  is  given  in  chapter 
three.  In  form  this  lake  resembled  Temagami  in  its  spider-like  arms,  its 
long  shore  line  and  its  small  area  in  Pennsylvania.  It  is  the  interpreter 
of  the  Tionesta  (old  Middle  Allegheny)  glacial  history. 

Period  One  extends  from  its  separation  from  the  main  ponding,  in 
front  of  the  main  trunk  of  the  ice-sheet,  to  its  discharge  over  the  Foxburg 
col.  This  period  followed  the  first  of  Lake  Wright  by  the  interval  neces- 
sary to  pass  from  the  old  Allegheny  to  the  old  Tionesta  mouth  in  Erigan 
Valley.  The  contemporary  events  are: 

Trenching  of  Barnesville  col  to  1440. 

Discharge  of  Upper  Oil  Creek  drainage  over  Titusville  col. 

Deposition  of  clays  in  Lower  Oil  Creek  Valley. 

Beginning  of  the  trenching  of  Thompsons  col. 

Drainage  of  lake  through  marginal  canyon,  and  no  glacial  overwash  sent  up  the 
flooded  Tionesta.  Overwash  from  Titusville,  Thompsons  and  Barnesville. 

(?)  At  the  end  of  this  period  the  lake  level  backed  up  over  Barnesville,  so  that  the 
upper  sands  at  Clarendon  were  smoothed  at  1443. 

The  following  deposits  can  not  be  synchronized,  as  they  are  discon- 
nected with  one  another,  and  with  those  of  Lake  Wright.  The  3  feet  of 
blued  clay  against  the  rock  floor  at  Oil  City  came  from  the  deforestation  of 
the  Upper  Oil  Creek  basin.  It  is  overlaid  by  the  yellowish  sandy  clay  cap 
with  local  enclosures.  Between  Petroleum  Center  and  Plumer  the  lower 
clay  is  mottled  and  streaked,  bluish-yellowish-whitish-brown,  enclosing 
flakes  of  shale,  pitted,  abounding  in  shots  of  limonite,  and  the  clay  itself 
is  filled  with  nodules  of  the  mineral.  This  is  denser  than  the  sandy  drift 
above  it.  At  Franklin  the  blued  clay  is  overlaid  with  red  silt  enclosing 
local  gravel  of  red  color,  as  shown  in  the  trench  for  the  water  main  which 
extends  from  water  level  to  1500  feet  above  ocean  level — a  total  of  500 
(vertical)  feet.  Above  the  level  of  the  stream  bed  the  silty  wash  against 
the  rock  floor  is  overlaid  by  gravelly  drift,  and  this  is  found  on  the  hill 
south  of  the  town.. 

Period  Two  covers  the  trenching  of  Foxburg  col  from  1450  to  1300. 
The  contemporary  events  are: 

The  trenching  of  Barnesville  col  to  1300. 

The  trenching  of  Titusville  and  Thompsons  cols  to  permit  the  passage  of  gravels. 

The  discharge  of  the  greater  part  of  the  glacial  ablation  through  the  marginal 
canyon,  with  a  slight  flow  up  the  Tionesta  from  the  ice-margin  to  bring  sands  to 
Franklin — perhaps  through  Sugar  Creek. 

iJThe  discharge  of  the  regional  drainage  over  Foxburg  col  through  West   Sandy 
Creek  by  reversal  of  drainage. 

The  water-laid  drift  at  Tidioute  was  dropped  on  the  slack-water 
side  of  the  channel  up  to  1420:  on  the  current  side,  to  1300.  The  gravel 
is  similar  to  that  of  the  bar  opposite  the  mouth  of  Brokenstraw  Creek. 
This  same  gravel  forms  the  bar  across  the  mouth  of  Tionesta  River  at 


96  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

its  confluence  with  the  present  Allegheny.  It  does  not  exist  in  the 
stream  above  or  on  either  side  of  Barnesville  col.  The  gravel  beds 
below  Tionesta  probably  belong  to  this  period,  as  a  starting  point,  with 
a  finish  later.  Here  also  began  the  filling  back  of  Egbert  Hill,  and  that 
in  West  Sandy  Valley  from  Takitezy  southward. 

Period  Three  begins  with  the  flow  over  Fosters  col,  and  ends  with 
this  and  Foxburg  col  trenched  to  their  present  rock  floors.  The  con- 
temporary events  are: 

The  arrival  of  the  ice-margin  across  the  mouth  of  West  Sandy  Creek,  and  its 
progress  to  its  farthest  extent. 

The  complete  closing  of  West  Sandy  Creek  mouth,  and  the  temporary  stoppage  of 
all  flow  through  it  and  over  Foxburg  col  other  than  that  from  the  ablation  of  the 
ice  in  and  to  the  west  of  West  Sandy  basin. 

The  rise  of  the  lake  level  to  that  of  the  lowest  rol  (Fosters),  (1500). 

The  reversal  of  flow  in  East  Sandy  Creek  Valley. 

The  passage  of  the  torrent  (combined  flow  from  Barnesville,  Thompsons  and 
Titusville)  at  1500  across  the  old  divide  from  Egbert  Hill  southeastward. 

The  trenching  of  the  old  divide  to  present  water  level. 

The  completion  of  the  filling  back  of  Egbert  Hill. 

The  backing  up  of  the  water  at  1500  about  Warren,  Titusville,  Clarendon,  Sala- 
manca, Olean,  and  Port  Allegany.  The  development  of  beach-lines,  terraces,  swamps, 
etc.,  from  1500  to  1450, 

The  filling  of  Barnesville  trench  with  gravel. 

The  deposition  of  Leverett  clay  as  above  noted. 

The  clearing  of  the  main  channel  from  stagnant  ice. 

The  arrival  of  the  marginal  torrent  seems  to  have  been  contempora- 
neous with  that  of  the  ice-margin  as  a  stopper  across  West  Sandy 
Valley  mouth.  That  margin  extended  across  Oil  Creek,  opening  fan- 
wise  with  the  center  of  motion  on  the  highlands  of  McKean  County. 
This  would  bring  the  ice-margin  and  the  marginal  torrent  across  the  col 
at  Fosters.  Its  elevation  was  probably  1500,  as  its  sheer  walls  rise  to 
nearly  that  elevation  today — the  south  one,  against  which  the  torrent 
hurled  itself,  being  the  more  steep.  The  recency  of  the  trenching  of 
the  old  divide  back  of  Egbert 's  Hill  is  shown  in  Figure  52.  On  the  sheer 
walls  are  deposits  of  dense  cobbly  drift,  with  the  cobbles  highly  polished. 
The  trenching  thus  preceded  the  drift-sheet.  The  depth  of  flooding 
is  shown  by  the  height  of  iceberg  action.  In  the  sands  we  find  stones 
from  ice-cakes.  One  of  them  at  1500,  on  top  of  the  hill  south  of  Franklin 
in  sand  was  a  piece  of  red  granite  with  quarry  face  and  no  sign  of 
glaciation.  It  did  not  come  in  the  ice-sheet,  as  it  was  so  decayed  as  to 
be  friable  and  even  pulverulent.  It  is  difficult  to  see  how  it  escaped 
crushing.  Near  it  was  a  fresh  cobble  of  black  gneiss  similarly  left.  This 
latter  rock  was  found  at  intervals  nearer  Franklin  and  at  lower  elevations. 
Beginning  at  the  north,  we  find  Leverett  clay  at  and  above  1400  as  far  as 
Fosters :  below  we  find  it  up  to  1300.  The  Sheffield  terrace,  the  Roystone 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 


97 


delta  and  swamp  are  1442-1450.     The  Clarendon  swamp,  1400.     The 
top  of  the  highest  terrace  in  Barnesville  trench,  1360.     Figure  53  shows 


FIG.  52. — Sheer  walls  of  trench  through  "Old  Divide"  lined  and  capped  by  drift, 

Franklin,  Venango,  Co. 


FIG.  53. — Orogenic  drift  beneath  Leverett  clay,  Roystone,  Warren  Co. 

the  local  drift  beneath  clay  2  miles  east  of  Roystone.  Figure  54  shows 
the  surface  of  the  clay  and  the  trash  brought  from  Kane  by  ice-cakes. 
The  cleared  surface  of  the  South  Warren  gravels,  Figure  48,  indicates 


98 


PENNSYLVANIA  GLACIATION.    FIRST  PHASE 


at  least  10  to  12  feet  of  Leverett  clay.  At  the  end  of  this  terrace-bar 
(Figure  51)  this  clay  is  less  than  2  feet  thick.  It  is  not  a  slope  wash, 
either  here  or  at  the  Oakland  Cemetery,  as  both  stand  out  into  the  plain 
and  rise  from  it  on  all  sides.  The  thinness  of  the  clay  at  the  ends  of  each 
is  caused  by  the  nearness  of  the  current,  which  prevented  as  thick  a 
deposition  of  strata  as  nearer  the  protection  of  the  wedge-end  behind 
which  the  slackened  water  obtained.  There  is  thus  the  same  thinning 
out  of  strata  as  shown  in  Figure  41  for  the  Indian  Hollow  deposits,  and 
the  same  shaping  of  deposits  at  the  time  of  deposition.  The  proximity 
to  the  current  also  prevented  the  lingering  or  accumulation  of  icebergs 
and  cakes,  and  thus  the  Leverett  clay  is  mainly  a  clean  sand  here,  free 
from  inclusions. 


FIG.  54. — Iceberg  burden  in  Leverett  clay,  surface  at  Roystone,  Warren  Co. 

The  coarse  gravels  at  Sheffield  belong  to  the  commencement  of  this 
period,  if  not  to  the  middle  and  end  of  the  last.  They  came  from  Kane 
during  the  presence  of  the  ice  there,  and  by  them  Barnesville  col  was 
trenched.  The  other  gravels  of  this  period  are  found  about  and  below 
Franklin,  and  are  also  of  the  bar  type,  but  dropped  in  water  whose 
depth  was  greater  in  proportion  to  the  average  elevation  of  the  region 
above  ocean  level,  as  the  Franklin  crests  do  not  rise  much  over  100  feet 
above  the  highest  ponded  water,  while  those  about  Warren  rise  over 
500  feet  above.  Flooding  about  Franklin  meant,  therefore,  a  submerg- 
ence of  the  lesser  ridges,  a  short-cutting  of  currents  entirely  away  from 
the  preglacial  channels,  a  formation  of  areas  of  slackened  currents  which 
would  invite  deposition  indifferently  over  former  channels,  and  along 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK 


99 


hillsides  at  all  elevations.  As  cols  were  trenched  and  water  levels 
fell  there  would  be  a  shaping  of  these  deposits  to  present  forms,  and  a 
capping  by  washes  of  various  origins. 


FIG.  55. — Drift  overlaid  by  assorted  gravels.  Brandon,  Venango  Co. 


FIG.  56. — Thinness  of  Leverett  clay  over  assorted  gravels,  Kennerdell,  Venango  Co. 

The  Brandon  and  Kennerdell  deposits  are  good  examples,  as  they  are 
but  4  miles  apart,  but  at  different  elevations.     The  Franklin  quadrangle 


100  PENNSYLVANIA  GLACIATION.    FIRST  PHASE 

shows  their  location,  the  valley  cross-sections,  and  their  relation  to  the 
regional  cols.  The  valley  breadth  at  Brandon  is  six  times  that  at  Kenner- 
dell.  The  current  velocity  is  correspondingly  lower.  The  deposits  came 
after  the  clearance  of  the  channel  from  stagnant  ice,  and  with  Foxburg 
col  at  1300  above  ocean  level.  There  is  gradual  decrease  in  the  sizes 
of  the  pieces  from  Brandon  to  Kennerdell,  the  coarse  gravels  and  the 
thickest  clays  being  at  the  former.  They  are  dropped  on  top  of  the  land- 
laid  drift,  which  is  shown  at  Brandon  in  Figure  55  beneath  the  gravels. 
The  coarse  gravels  extend  at  this  place  to  1200  above  ocean  level,  and  200 
feet  above  their  top  at  Kennerdell,  where  the  deposit  between  1000  and 
1100  is  composed  of  fine  gravel  and  silt.  At  Brandon  there  is  sand  with 
50  per  cent,  gravel  between  1200  and  1300;  at  Kennerdell  this  is  found 
between  1100  and  1200.  On  each  is  a  sporadic  angular  wash  with  1 
per  cent,  of  gravel,  reaching  1400  feet  at  Brandon  and  1300  at  Kennerdell. 
The  Lever ett  clay  at  Brandon  varies  from  8  to  an  average  of  5  feet;  at 
Kennerdell,  2  feet,  as  shown  by  Figure  56.  There  is  thus  no  valley 
filled  with  gravel  by  ordinary  agencies,  and  with  subsequent  erosion. 
The  portion  between  Polk  and  Takitezy  shows  by  its  irregular  surface 
the  action  of  an  ice-sheet. 

There  was  no  regular  valley  filling  below  Foxburg  as  shown  by  the 
difference  in  elevation  of  gravel  on  opposite  sides  of  the  river  at  the  fol- 
lowing places.  The  first  figures  are  the  instrumental  elevations  of  gravel 
on  the  east  side;  the  second,  on  the  west.  Foxburg,  1135-1230;  Monterey, 
1125-1078;  East  Brady,  1115-1231;  Red  Bank,  1100-1060.  It  seems 
that  these  gravels  are  washes  carried  by  torrential  currents  with  ice-cakes 
to  such  elevations  as  the  regional  contours  favored.  This  case  is  like 
that  in  the  Juniata  Valley. 

The  Border  of  the  Ice-sheet. — The  land-laid  drift  north  of  Thompsons 
must  be  found  above  1600  to  show  freedon  from  ponded  water,  stranded 
bergs  and  beach  lines.  It  is  always  modified  by  the  washings  of  the 
ridges  during  the  ablation  of  the  stagnant  ice — a  washing  of  greater  impor- 
tance than  in  the  east,  as  the  ridges  are  thinner,  and  the  slopes  steeper, 
so  that  the  drift  is  washed  into  and  accumulated  in  the  valleys.  The 
presence  of  crystallines  was  made  a  sine  qua  non  in  the  determination 
of  drift  at  the  following  places.  Except  at  Clarendon  and  Foxburg, 
the  actual  edge  of  the  Attenuated  Border  was  not  found.  The  best  that 
can  be  said  of  the  other  places  is  that  the  ice  was  there,  and  may  have 
gone  beyond.  Below  Foxburg  there  is  a  general  submergence  and  a 
general  washing  which  makes  the  location  of  the  Border  very  difficult. 
In  so  brief  a  reconnaissance  as  was  permitted  the  writer  during  the  few 
weeks  of  each  year,  only  the  points  most  easy  of  access  were  reached. 
The  boundary  has  been  drawn  to  Kane  and  Clarendon,  with  an  apex 
south  of  that  at  Salamanca.  Thence  it  will  be  drawn  through  the 
following  places: 


SOUTHERN  MARGIN  OF  THE  MAIN  TRUNK  101 

Cobham. — Three  miles  east  of  Allegheny  River,  at  1700,  a  drift- 
sheet  of  red  silt  including  angular  and  rolled  cobbles  and  some  gravel, 
carried  along  ridge-crest  3  miles  east  of  river,  and  also  south  to  Tidioute. 

Hickory. — Granite  cobbles  are  reported  on  the  ridge  east  of  the  above 
river. 

South  Oil  City. — Drift  beneath  Lever ett  clay  1J^  miles  south  of  the 
river  at  1460.  At  higher  elevations  to  the  south  red  granite  appears  in 
the  field  cullings.  At  1520  red  silt  drift  on  sandstone  includes  sandstone 
pieces  harder  than  the  rock  floor.  The  rolled  pieces  are  less  than  one  in 
one  million. 

Coal  City. — Two  miles  east  of  Brandon  at  1561  is  a  surface  of  drift 
similar  to  that  about  Kane,  but  with  rounded  cobbles  and  boulders. 
These  last  differentiate  this  from  the  gravels,  which  carry  no  boulders, 
see  Figure  55. 

Foxburg. — This  is  south  of  the  col,  and  the  average  water  level  is 
1200.  On  the  St.  Petersburg  road  at  1170  the  scoured  rock  floor  is  capped 
with  2  feet  of  drift  (silt)  enclosing  foreign  rocks.  This  continues  over  one 
crest  and  to  the  top  of  the  next  at  1320,  covering  a  coal  outcrop.  Below 
the  last  crest  pieces  of  black  gneiss  and  basalt  were  found,  and  coal 
flakes  from  the  outcrop  were  carried  up  hill.  The  drift  ends  on  the  crest, 
and  beyond  it  the  rock  is  decaying  in  place. 

These  points  are  thus  distant  from  the  great  moraine:  Clarendon, 
17  miles;  Cobham,  17;  Tidioute,  15;  Hickory,  19;  South  Oil  City,  14; 
Coal  City,  10;  Foxburg,  22.  The  boundary  of  the  Attenuated  Border 
is  thus  everywhere  east  of  Allegheny  River  from  Clarendon  to  Foxburg, 
with  an  average  of  17  miles  from  the  great  moraine.  This  completes 
the  parallelism  between  the  two,  and  prompts  the  question  whether 
these  are  not  results  of  different  phases  of  the  same  ice-sheet. 


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